Add missing function for FormValidator filters - refs BT#22293

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

@@ -1988,3 +1988,30 @@ function mobile_phone_number_filter($mobilePhoneNumber)
 
     return ltrim($mobilePhoneNumber, '0');
 }
+
+/**
+ * Cleans JS from a URL.
+ *
+ * @param string $html URL to clean
+ * @param int    $mode (optional)
+ *
+ * @return string The cleaned URL
+ */
+function plain_url_filter($html, $mode = NO_HTML)
+{
+    $allowed_tags = HTML_QuickForm_Rule_HTML::get_allowed_tags($mode);
+    $html = kses_no_null($html);
+    $html = kses_js_entities($html);
+    $allowed_html_fixed = kses_array_lc($allowed_tags);
+
+    return kses_split($html, $allowed_html_fixed, ['http', 'https']);
+}
+
+/**
+ * Prevent execution of event handlers in HTML elements.
+ */
+function attr_on_filter(string $html): string
+{
+    return RemoveOnAttributes::filter($html);
+}
+