diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2ab3015..9746644 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,25 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.4.9] - 2026-02-26
+
+### Security
+
+- Fixed XSS vulnerability: replaced all jQuery `.html()` injections with safe `.text()` DOM construction in admin.js
+- Fixed insecure token generation: replaced `Math.random()` with `crypto.getRandomValues()` (Web Crypto API)
+- Fixed XSS via string interpolation in `updateValueRows()`: replaced HTML string building with jQuery DOM construction
+- Added 1 MB import size limit to prevent DoS via large JSON payloads in CustomMetricBuilder
+- Removed `site_url` from metric export data to prevent information disclosure
+- Added import mode validation (allowlist check) in CustomMetricBuilder
+
+### Changed
+
+- Extracted shared authentication logic (`wp_prometheus_authenticate_request()`) to eliminate code duplication between MetricsEndpoint and isolated mode handler
+- Extracted `showNotice()` helper in admin.js to DRY up 10+ duplicated AJAX response handling patterns
+- Extracted `is_hpos_enabled()` helper method in Collector to DRY up WooCommerce HPOS checks
+- Optimized WooCommerce product type counting: uses `paginate: true` COUNT query instead of loading all product IDs into memory
+- Added missing options to `Installer::uninstall()` cleanup (isolated_mode, storage adapter, Redis/APCu config)
+
 ## [0.4.8] - 2026-02-07
 
 ### Fixed
diff --git a/assets/js/admin.js b/assets/js/admin.js
index 8f98aff..ecc0fad 100644
--- a/assets/js/admin.js
+++ b/assets/js/admin.js
@@ -235,31 +235,19 @@
                 $spinner.removeClass('is-active');
 
                 if (response.success) {
-                    $message
-                        .removeClass('notice-error')
-                        .addClass('notice notice-success')
-                        .html('<p>' + response.data.message + '</p>')
-                        .show();
+                    showNotice($message, response.data.message, 'success');
 
                     // Reload page after successful validation/activation.
                     setTimeout(function() {
                         location.reload();
                     }, 1500);
                 } else {
-                    $message
-                        .removeClass('notice-success')
-                        .addClass('notice notice-error')
-                        .html('<p>' + (response.data.message || 'An error occurred.') + '</p>')
-                        .show();
+                    showNotice($message, response.data.message || 'An error occurred.', 'error');
                 }
             },
             error: function() {
                 $spinner.removeClass('is-active');
-                $message
-                    .removeClass('notice-success')
-                    .addClass('notice notice-error')
-                    .html('<p>Connection error. Please try again.</p>')
-                    .show();
+                showNotice($message, 'Connection error. Please try again.', 'error');
             }
         });
     }
@@ -287,30 +275,18 @@
                 $spinner.removeClass('is-active');
 
                 if (response.success) {
-                    $message
-                        .removeClass('notice-error')
-                        .addClass('notice notice-success')
-                        .html('<p>' + response.data.message + '</p>')
-                        .show();
+                    showNotice($message, response.data.message, 'success');
 
                     setTimeout(function() {
                         window.location.href = window.location.pathname + '?page=wp-prometheus&tab=custom';
                     }, 1000);
                 } else {
-                    $message
-                        .removeClass('notice-success')
-                        .addClass('notice notice-error')
-                        .html('<p>' + (response.data.message || 'An error occurred.') + '</p>')
-                        .show();
+                    showNotice($message, response.data.message || 'An error occurred.', 'error');
                 }
             },
             error: function() {
                 $spinner.removeClass('is-active');
-                $message
-                    .removeClass('notice-success')
-                    .addClass('notice notice-error')
-                    .html('<p>Connection error. Please try again.</p>')
-                    .show();
+                showNotice($message, 'Connection error. Please try again.', 'error');
             }
         });
     }
@@ -398,11 +374,7 @@
                 $spinner.removeClass('is-active');
 
                 if (response.success) {
-                    $message
-                        .removeClass('notice-error')
-                        .addClass('notice notice-success')
-                        .html('<p>' + response.data.message + '</p>')
-                        .show();
+                    showNotice($message, response.data.message, 'success');
 
                     $('#import-options').slideUp();
                     $('#import-metrics-file').val('');
@@ -412,20 +384,12 @@
                         location.reload();
                     }, 1500);
                 } else {
-                    $message
-                        .removeClass('notice-success')
-                        .addClass('notice notice-error')
-                        .html('<p>' + (response.data.message || 'An error occurred.') + '</p>')
-                        .show();
+                    showNotice($message, response.data.message || 'An error occurred.', 'error');
                 }
             },
             error: function() {
                 $spinner.removeClass('is-active');
-                $message
-                    .removeClass('notice-success')
-                    .addClass('notice notice-error')
-                    .html('<p>Connection error. Please try again.</p>')
-                    .show();
+                showNotice($message, 'Connection error. Please try again.', 'error');
             }
         });
     }
@@ -478,26 +442,14 @@
                 $spinner.removeClass('is-active');
 
                 if (response.success) {
-                    $message
-                        .removeClass('notice-error')
-                        .addClass('notice notice-success')
-                        .html('<p>' + response.data.message + '</p>')
-                        .show();
+                    showNotice($message, response.data.message, 'success');
                 } else {
-                    $message
-                        .removeClass('notice-success')
-                        .addClass('notice notice-error')
-                        .html('<p>' + (response.data.message || 'An error occurred.') + '</p>')
-                        .show();
+                    showNotice($message, response.data.message || 'An error occurred.', 'error');
                 }
             },
             error: function() {
                 $spinner.removeClass('is-active');
-                $message
-                    .removeClass('notice-success')
-                    .addClass('notice notice-error')
-                    .html('<p>Connection error. Please try again.</p>')
-                    .show();
+                showNotice($message, 'Connection error. Please try again.', 'error');
             }
         });
     }
@@ -546,15 +498,30 @@
             // Remove all inputs except the value and button.
             $row.find('input').remove();
 
-            // Re-add label inputs.
+            // Re-add label inputs using safe DOM construction.
             for (var i = 0; i < labelCount; i++) {
                 var val = currentValues[i] || '';
-                $row.prepend('<input type="text" name="label_values[' + rowIndex + '][]" class="small-text" placeholder="' + (labels[i] || 'value') + '" value="' + val + '">');
+                var $input = $('<input>', {
+                    type: 'text',
+                    name: 'label_values[' + rowIndex + '][]',
+                    'class': 'small-text',
+                    placeholder: labels[i] || 'value',
+                    value: val
+                });
+                $row.prepend($input);
             }
 
-            // Re-add value input.
+            // Re-add value input using safe DOM construction.
             var metricVal = currentValues[currentValues.length - 1] || '';
-            $row.find('.remove-value-row').before('<input type="number" name="label_values[' + rowIndex + '][]" class="small-text" step="any" placeholder="Value" value="' + metricVal + '">');
+            var $valueInput = $('<input>', {
+                type: 'number',
+                name: 'label_values[' + rowIndex + '][]',
+                'class': 'small-text',
+                step: 'any',
+                placeholder: 'Value',
+                value: metricVal
+            });
+            $row.find('.remove-value-row').before($valueInput);
         });
     }
 
@@ -584,7 +551,7 @@
     }
 
     /**
-     * Generate a random token.
+     * Generate a cryptographically secure random token.
      *
      * @param {number} length Token length.
      * @return {string} Generated token.
@@ -592,12 +559,31 @@
     function generateToken(length) {
         var charset = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789';
         var token = '';
+        var randomValues = new Uint32Array(length);
+        window.crypto.getRandomValues(randomValues);
         for (var i = 0; i < length; i++) {
-            token += charset.charAt(Math.floor(Math.random() * charset.length));
+            token += charset.charAt(randomValues[i] % charset.length);
         }
         return token;
     }
 
+    /**
+     * Show a notice message safely (XSS-safe).
+     *
+     * @param {jQuery}  $element  The message container element.
+     * @param {string}  message   The message text.
+     * @param {string}  type      Notice type: 'success', 'error', or 'warning'.
+     */
+    function showNotice($element, message, type) {
+        var removeClasses = 'notice-error notice-success notice-warning';
+        $element
+            .removeClass(removeClasses)
+            .addClass('notice notice-' + type)
+            .empty()
+            .append($('<p>').text(message))
+            .show();
+    }
+
     /**
      * Download a file.
      *
@@ -666,12 +652,8 @@
                 $spinner.removeClass('is-active');
 
                 if (response.success) {
-                    var noticeClass = response.data.warning ? 'notice-warning' : 'notice-success';
-                    $message
-                        .removeClass('notice-error notice-success notice-warning')
-                        .addClass('notice ' + noticeClass)
-                        .html('<p>' + response.data.message + '</p>')
-                        .show();
+                    var type = response.data.warning ? 'warning' : 'success';
+                    showNotice($message, response.data.message, type);
 
                     if (!response.data.warning) {
                         setTimeout(function() {
@@ -679,20 +661,12 @@
                         }, 1500);
                     }
                 } else {
-                    $message
-                        .removeClass('notice-success notice-warning')
-                        .addClass('notice notice-error')
-                        .html('<p>' + (response.data.message || 'An error occurred.') + '</p>')
-                        .show();
+                    showNotice($message, response.data.message || 'An error occurred.', 'error');
                 }
             },
             error: function() {
                 $spinner.removeClass('is-active');
-                $message
-                    .removeClass('notice-success notice-warning')
-                    .addClass('notice notice-error')
-                    .html('<p>Connection error. Please try again.</p>')
-                    .show();
+                showNotice($message, 'Connection error. Please try again.', 'error');
             }
         });
     }
@@ -720,26 +694,14 @@
                 $spinner.removeClass('is-active');
 
                 if (response.success) {
-                    $message
-                        .removeClass('notice-error notice-warning')
-                        .addClass('notice notice-success')
-                        .html('<p>' + response.data.message + '</p>')
-                        .show();
+                    showNotice($message, response.data.message, 'success');
                 } else {
-                    $message
-                        .removeClass('notice-success notice-warning')
-                        .addClass('notice notice-error')
-                        .html('<p>' + (response.data.message || 'Connection test failed.') + '</p>')
-                        .show();
+                    showNotice($message, response.data.message || 'Connection test failed.', 'error');
                 }
             },
             error: function() {
                 $spinner.removeClass('is-active');
-                $message
-                    .removeClass('notice-success notice-warning')
-                    .addClass('notice notice-error')
-                    .html('<p>Connection error. Please try again.</p>')
-                    .show();
+                showNotice($message, 'Connection error. Please try again.', 'error');
             }
         });
     }
diff --git a/src/Endpoint/MetricsEndpoint.php b/src/Endpoint/MetricsEndpoint.php
index 9cbce84..0e3711a 100644
--- a/src/Endpoint/MetricsEndpoint.php
+++ b/src/Endpoint/MetricsEndpoint.php
@@ -102,52 +102,12 @@ class MetricsEndpoint {
     /**
      * Authenticate the metrics request.
      *
+     * Uses the shared authentication helper to avoid code duplication
+     * with the isolated mode handler in wp-prometheus.php.
+     *
      * @return bool
      */
     private function authenticate(): bool {
-        $auth_token = get_option( 'wp_prometheus_auth_token', '' );
-
-        // If no token is set, deny access.
-        if ( empty( $auth_token ) ) {
-            return false;
-        }
-
-        // Check for Bearer token in Authorization header.
-        $auth_header = $this->get_authorization_header();
-        if ( ! empty( $auth_header ) && preg_match( '/Bearer\s+(.*)$/i', $auth_header, $matches ) ) {
-            return hash_equals( $auth_token, $matches[1] );
-        }
-
-        // Check for token in query parameter (less secure but useful for testing).
-        // phpcs:ignore WordPress.Security.NonceVerification.Recommended -- Auth token check.
-        if ( isset( $_GET['token'] ) && hash_equals( $auth_token, sanitize_text_field( wp_unslash( $_GET['token'] ) ) ) ) {
-            return true;
-        }
-
-        return false;
-    }
-
-    /**
-     * Get the Authorization header from the request.
-     *
-     * @return string
-     */
-    private function get_authorization_header(): string {
-        if ( isset( $_SERVER['HTTP_AUTHORIZATION'] ) ) {
-            return sanitize_text_field( wp_unslash( $_SERVER['HTTP_AUTHORIZATION'] ) );
-        }
-
-        if ( isset( $_SERVER['REDIRECT_HTTP_AUTHORIZATION'] ) ) {
-            return sanitize_text_field( wp_unslash( $_SERVER['REDIRECT_HTTP_AUTHORIZATION'] ) );
-        }
-
-        if ( function_exists( 'apache_request_headers' ) ) {
-            $headers = apache_request_headers();
-            if ( isset( $headers['Authorization'] ) ) {
-                return sanitize_text_field( $headers['Authorization'] );
-            }
-        }
-
-        return '';
+        return wp_prometheus_authenticate_request();
     }
 }
diff --git a/src/Installer.php b/src/Installer.php
index eb1eff0..54e35c8 100644
--- a/src/Installer.php
+++ b/src/Installer.php
@@ -65,6 +65,14 @@ final class Installer {
             'wp_prometheus_enabled_metrics',
             'wp_prometheus_runtime_metrics',
             'wp_prometheus_custom_metrics',
+            'wp_prometheus_isolated_mode',
+            'wp_prometheus_storage_adapter',
+            'wp_prometheus_redis_host',
+            'wp_prometheus_redis_port',
+            'wp_prometheus_redis_password',
+            'wp_prometheus_redis_database',
+            'wp_prometheus_redis_prefix',
+            'wp_prometheus_apcu_prefix',
         );
 
         foreach ( $options as $option ) {
diff --git a/src/Metrics/Collector.php b/src/Metrics/Collector.php
index 8de12fd..64f2851 100644
--- a/src/Metrics/Collector.php
+++ b/src/Metrics/Collector.php
@@ -447,6 +447,16 @@ class Collector {
         return class_exists( 'WooCommerce' );
     }
 
+    /**
+     * Check if WooCommerce HPOS (High-Performance Order Storage) is enabled.
+     *
+     * @return bool
+     */
+    private function is_hpos_enabled(): bool {
+        return class_exists( '\Automattic\WooCommerce\Utilities\OrderUtil' )
+            && \Automattic\WooCommerce\Utilities\OrderUtil::custom_orders_table_usage_is_enabled();
+    }
+
     /**
      * Collect WooCommerce metrics.
      *
@@ -498,16 +508,17 @@ class Collector {
             }
         }
 
-        // Count by product type (for published products only).
+        // Count by product type (for published products only) using count query.
         foreach ( array_keys( $product_types ) as $type ) {
             $args = array(
                 'status' => 'publish',
                 'type'   => $type,
-                'limit'  => -1,
+                'limit'  => 1,
                 'return' => 'ids',
+                'paginate' => true,
             );
-            $products = wc_get_products( $args );
-            $gauge->set( count( $products ), array( 'publish', $type ) );
+            $result = wc_get_products( $args );
+            $gauge->set( $result->total, array( 'publish', $type ) );
         }
     }
 
@@ -553,8 +564,7 @@ class Collector {
         $currency = get_woocommerce_currency();
 
         // Check if HPOS (High-Performance Order Storage) is enabled.
-        $hpos_enabled = class_exists( '\Automattic\WooCommerce\Utilities\OrderUtil' )
-            && \Automattic\WooCommerce\Utilities\OrderUtil::custom_orders_table_usage_is_enabled();
+        $hpos_enabled = $this->is_hpos_enabled();
 
         if ( $hpos_enabled ) {
             $orders_table = $wpdb->prefix . 'wc_orders';
diff --git a/src/Metrics/CustomMetricBuilder.php b/src/Metrics/CustomMetricBuilder.php
index 0632d45..6129ed7 100644
--- a/src/Metrics/CustomMetricBuilder.php
+++ b/src/Metrics/CustomMetricBuilder.php
@@ -47,6 +47,13 @@ class CustomMetricBuilder {
 	 */
 	const MAX_LABEL_VALUES = 50;
 
+	/**
+	 * Maximum import JSON size in bytes (1 MB).
+	 *
+	 * @var int
+	 */
+	const MAX_IMPORT_SIZE = 1048576;
+
 	/**
 	 * Get all custom metrics.
 	 *
@@ -332,7 +339,6 @@ class CustomMetricBuilder {
 			'version'        => self::EXPORT_VERSION,
 			'plugin_version' => WP_PROMETHEUS_VERSION,
 			'exported_at'    => gmdate( 'c' ),
-			'site_url'       => home_url(),
 			'metrics'        => array_values( $metrics ),
 		);
 
@@ -348,6 +354,17 @@ class CustomMetricBuilder {
 	 * @throws \InvalidArgumentException If JSON is invalid.
 	 */
 	public function import( string $json, string $mode = 'skip' ): array {
+		// Prevent DoS via excessively large imports.
+		if ( strlen( $json ) > self::MAX_IMPORT_SIZE ) {
+			throw new \InvalidArgumentException(
+				sprintf(
+					/* translators: %s: Maximum size */
+					__( 'Import data exceeds maximum size of %s.', 'wp-prometheus' ),
+					size_format( self::MAX_IMPORT_SIZE )
+				)
+			);
+		}
+
 		$data = json_decode( $json, true );
 
 		if ( json_last_error() !== JSON_ERROR_NONE ) {
@@ -358,6 +375,12 @@ class CustomMetricBuilder {
 			throw new \InvalidArgumentException( __( 'No metrics found in import file.', 'wp-prometheus' ) );
 		}
 
+		// Validate import mode.
+		$valid_modes = array( 'skip', 'overwrite', 'rename' );
+		if ( ! in_array( $mode, $valid_modes, true ) ) {
+			$mode = 'skip';
+		}
+
 		$result = array(
 			'imported' => 0,
 			'skipped'  => 0,
diff --git a/wp-prometheus.php b/wp-prometheus.php
index d906ebb..d5af869 100644
--- a/wp-prometheus.php
+++ b/wp-prometheus.php
@@ -107,36 +107,8 @@ function wp_prometheus_isolated_metrics_handler(): void {
         return; // Let normal flow handle unlicensed state.
     }
 
-    // Authenticate.
-    $auth_token = get_option( 'wp_prometheus_auth_token', '' );
-    if ( empty( $auth_token ) ) {
-        status_header( 401 );
-        header( 'WWW-Authenticate: Bearer realm="WP Prometheus Metrics"' );
-        header( 'Content-Type: text/plain; charset=utf-8' );
-        echo 'Unauthorized';
-        exit;
-    }
-
-    // Check Bearer token.
-    $auth_header = '';
-    if ( isset( $_SERVER['HTTP_AUTHORIZATION'] ) ) {
-        $auth_header = sanitize_text_field( wp_unslash( $_SERVER['HTTP_AUTHORIZATION'] ) );
-    } elseif ( isset( $_SERVER['REDIRECT_HTTP_AUTHORIZATION'] ) ) {
-        $auth_header = sanitize_text_field( wp_unslash( $_SERVER['REDIRECT_HTTP_AUTHORIZATION'] ) );
-    }
-
-    $authenticated = false;
-    if ( ! empty( $auth_header ) && preg_match( '/Bearer\s+(.*)$/i', $auth_header, $matches ) ) {
-        $authenticated = hash_equals( $auth_token, $matches[1] );
-    }
-
-    // Check query parameter fallback.
-    // phpcs:ignore WordPress.Security.NonceVerification.Recommended -- Auth token check.
-    if ( ! $authenticated && isset( $_GET['token'] ) ) {
-        $authenticated = hash_equals( $auth_token, sanitize_text_field( wp_unslash( $_GET['token'] ) ) );
-    }
-
-    if ( ! $authenticated ) {
+    // Authenticate using shared helper.
+    if ( ! wp_prometheus_authenticate_request() ) {
         status_header( 401 );
         header( 'WWW-Authenticate: Bearer realm="WP Prometheus Metrics"' );
         header( 'Content-Type: text/plain; charset=utf-8' );
@@ -161,6 +133,64 @@ function wp_prometheus_isolated_metrics_handler(): void {
     exit;
 }
 
+/**
+ * Authenticate a metrics request using Bearer token or query parameter.
+ *
+ * Shared authentication logic used by both the MetricsEndpoint class
+ * and the isolated mode handler to avoid code duplication.
+ *
+ * @return bool True if authenticated, false otherwise.
+ */
+function wp_prometheus_authenticate_request(): bool {
+    $auth_token = get_option( 'wp_prometheus_auth_token', '' );
+
+    // If no token is set, deny access.
+    if ( empty( $auth_token ) ) {
+        return false;
+    }
+
+    // Check for Bearer token in Authorization header.
+    $auth_header = wp_prometheus_get_authorization_header();
+    if ( ! empty( $auth_header ) && preg_match( '/Bearer\s+(.*)$/i', $auth_header, $matches ) ) {
+        return hash_equals( $auth_token, $matches[1] );
+    }
+
+    // Check for token in query parameter (less secure but useful for testing).
+    // phpcs:ignore WordPress.Security.NonceVerification.Recommended -- Auth token check.
+    if ( isset( $_GET['token'] ) && hash_equals( $auth_token, sanitize_text_field( wp_unslash( $_GET['token'] ) ) ) ) {
+        return true;
+    }
+
+    return false;
+}
+
+/**
+ * Get the Authorization header from the request.
+ *
+ * Checks multiple sources for the Authorization header to support
+ * different server configurations (Apache, nginx, CGI, etc.).
+ *
+ * @return string The Authorization header value, or empty string if not found.
+ */
+function wp_prometheus_get_authorization_header(): string {
+    if ( isset( $_SERVER['HTTP_AUTHORIZATION'] ) ) {
+        return sanitize_text_field( wp_unslash( $_SERVER['HTTP_AUTHORIZATION'] ) );
+    }
+
+    if ( isset( $_SERVER['REDIRECT_HTTP_AUTHORIZATION'] ) ) {
+        return sanitize_text_field( wp_unslash( $_SERVER['REDIRECT_HTTP_AUTHORIZATION'] ) );
+    }
+
+    if ( function_exists( 'apache_request_headers' ) ) {
+        $headers = apache_request_headers();
+        if ( isset( $headers['Authorization'] ) ) {
+            return sanitize_text_field( $headers['Authorization'] );
+        }
+    }
+
+    return '';
+}
+
 // Try early metrics handling before full plugin initialization.
 wp_prometheus_early_metrics_check();