build canonical abs URL from admin URL

Author: himanshupathak95

src/wp-admin/includes/misc.php

@@ -1406,7 +1406,11 @@ function wp_admin_canonical_url() {
 	}
 
 	// Ensure we're using an absolute URL.
-	$current_url  = set_url_scheme( 'http://' . $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI'] );
+	// Build the canonical URL using the configured admin URL to avoid issues
+	// with reverse proxies that expose a different host via HTTP_HOST.
+	$path         = parse_url( $_SERVER['REQUEST_URI'], PHP_URL_PATH );
+	$query        = parse_url( $_SERVER['REQUEST_URI'], PHP_URL_QUERY );
+	$current_url  = admin_url( ltrim( $path, '/' ) . ( $query ? '?' . $query : '' ) );
 	$filtered_url = remove_query_arg( $removable_query_args, $current_url );
 
 	/**