Fix decoding of mailto: links with + character in HTML messages (#6020)

CHANGELOG

@@ -49,6 +49,7 @@ CHANGELOG Roundcube Webmail
 - Fix touch event issue on messages list in IE/Edge (#5781)
 - Fix so links over images are not removed in plain text signatures converted from HTML (#4473)
 - Fix various issues when downloading files with names containing non-ascii chars, use RFC 2231 (#5772)
+- Fix decoding of mailto: links with + character in HTML messages (#6020)
 
 RELEASE 1.3.2
 -------------

program/steps/mail/func.inc

@@ -1606,8 +1606,9 @@ function rcmail_washtml_link_callback($tag, $attribs, $content, $washtml)
     else if (preg_match('/^mailto:(.+)/i', $attrib['href'], $mailto)) {
         list($mailto, $url) = explode('?', html_entity_decode($mailto[1], ENT_QUOTES, 'UTF-8'), 2);
 
-        $url       = urldecode($url);
-        $mailto    = urldecode($mailto);
+        // #6020: use raw encoding for correct "+" character handling as specified in RFC6068
+        $url       = rawurldecode($url);
+        $mailto    = rawurldecode($mailto);
         $addresses = rcube_mime::decode_address_list($mailto, null, true);
         $mailto    = array();