CVE-2026-45118

Description

MyBB is free and open source forum software. Prior to 1.8.40, the Contact module does not validate a redirect URL or protocol correctly, resulting in an open redirect and reflected JavaScript code injection. contact.php accepts the redirect target from the from HTTP parameter in $mybb->input[-from-] or the Referer HTTP header in $_SERVER[-HTTP_REFERER-] and passes it to redirect() without sufficient verification. A javascript: URI becomes the target of the `Click here if you don-t want to wait any longer` link because $force_redirect is true, allowing script execution when a victim selects the link. This issue is fixed in version 1.8.40.