Ticket #40893: 40893.patch

src/wp-includes/class-wp-editor.php

@@ -527 +527 @@
                                 $editor_styles = get_editor_stylesheets();
 
                                 if ( ! empty( $editor_styles ) ) {
+                                        // Force urlencoding of commas
+                                        foreach ( $editor_styles as $key => $url ) {
+                                                if ( strpos( $url, ',' ) !== false ) {
+                                                        $editor_styles[$key] = str_replace( ',', '%2C', $url );
+                                                }
+                                        }
+
                                         $mce_css .= ',' . implode( ',', $editor_styles );
                                 }