As per the private.php XSS loophole, you need to patch newpm.php as well or else you can be hacked.
Manual Patch Instructions
In newpm.php, find the following:
PHP Code:
$pm['message'] = htmlspecialchars_uni($pm['message']);
BELOW it, add the following:
PHP Code:
$pm['recipients'] = htmlspecialchars_uni($pm['recipients']);
Refer to announcement here:
https://vborg.vbsupport.ru/showthread.php?t=74035