Global: Fix df47eac9b9 where the filter for "on" attributes was too wide and replaced normal text containing " on" - refs #5887

main/inc/lib/formvalidator/FormValidator.class.php

@@ -2111,5 +2111,5 @@ function attr_on_filter($html)
 {
     $prefix = uniqid('data-cke-').'-';
 
-    return preg_replace('/(\s)(on)/i', '$1'.$prefix.'$2', $html);
+    return preg_replace('/\b(on[a-z]+)\b\s*=/i', '$1'.$prefix.'$2', $html);
 }