Ticket #27601: 27601.1.diff

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

@@ -80 +80 @@
                 ) );
 
                 self::$this_tinymce = ( $set['tinymce'] && user_can_richedit() );
+
+                if ( self::$this_tinymce ) {
+                        if ( false !== strpos( $editor_id, '[' ) ) {
+                                self::$this_tinymce = false;
+                                _deprecated_argument( __METHOD__, '3.9', 'TinyMCE editor IDs cannot have brackets.' );
+                        }
+                }
+
                 self::$this_quicktags = (bool) $set['quicktags'];
 
                 if ( self::$this_tinymce )