org.xwiki.platform:xwiki-platform-wysiwyg-api Open Redirect vulnerability

Impact

An open redirect vulnerability in the HTML conversion request filter allows attackers to construct URLs on an XWiki instance that redirect to any URL. To reproduce, open <xwiki-host>/xwiki/bin/view/Main/?foo=bar&foo_syntax=invalid&RequiresHTMLConversion=foo&xerror=https://www.example.com/ where <xwiki-host> is the URL of your XWiki installation.

Patches

This bug has been fixed in XWiki 15.10.13, 16.4.4 and 16.8.0 by validating the domain of the redirect URL against the configured safe domains and the current request's domain.

Workarounds

A web application firewall could be configured to reject requests with the xerror parameter as from our analysis this parameter isn't used anymore. For requests with the RequiresHTMLConversion parameter set, the referrer URL should be checked if it points to the XWiki installation. Apart from that, we're not aware of any workarounds.