Ticket #37134: 37134.5.diff

src/wp-includes/kses.php

@@ -2300 +2300 @@
                         }
                 }
 
-                // Remove any CSS containing containing \ ( & } = or comments, except for url() useage checked above.
-                if ( $found && ! preg_match( '%[\\\(&=}]|/\*%', $css_test_string ) ) {
-                        if ( '' != $css ) {
-                                $css .= ';';
+                if ( $found ) {
+
+                        /**
+                         * Filters the regex limiting the list of characters not allowed in CSS rules.
+                         *
+                         * Default behaviour is to remove any css containing \ ( & } = or comments, except for url() usage.
+                         *
+                         * @since 5.5.0
+                         *
+                         * @param string $regex           Regex pattern of disallowed characters in CSS rules.
+                         * @param string $css_test_string CSS value to test.
+                         */
+                        $disallowed_chars = apply_filters( 'safe_style_disallowed_chars', '%[\\\(&=}]|/\*%', $css_test_string );
+                        if ( ! preg_match( $disallowed_chars, $css_test_string ) ) {
+                                if ( '' !== $css ) {
+                                        $css .= ';';
+                                }
+                                $css .= $css_item;
                         }
-
-                        $css .= $css_item;
                 }
         }