[6.0] Fix emailToPunycode() throws "Prohibited input U+0000005C" with backslash before quote

Resolves #46356

Author: janschoenherr

libraries/src/Filter/InputFilter.php

@@ -147,12 +147,12 @@ public function clean($source, $type = 'string')
      */
     public function emailToPunycode($text)
     {
-        $pattern = '/(("mailto:)+[\w\.\-\+]+\@[^"?]+\.+[^."?]+("|\?))/';
+        $pattern = '/("mailto:)([\w.\-+]+@[^"?]+\.+[^."?]+?)(\\\\?"|\?)/';
 
-        if (preg_match_all($pattern, $text, $matches)) {
-            foreach ($matches[0] as $match) {
-                $match  = (string) str_replace(['?', '"'], '', $match);
-                $text   = (string) str_replace($match, PunycodeHelper::emailToPunycode($match), $text);
+        if (preg_match_all($pattern, $text, $matches, PREG_SET_ORDER)) {
+            foreach ($matches as $match) {
+                $email = PunycodeHelper::emailToPunycode($match[2]);
+                $text  = str_replace($match[0], $match[1] . $email . $match[3], $text);
             }
         }