Semantic MediaWiki affected by Special:Ask table `sep` parameter reflected XSS

An unauthenticated attacker can inject HTML or script through the sep separator used in Special:Ask table output. The flaw affects both the standard page output and raw output requested with request_type=raw.

Look for mediawiki/semantic-media-wiki in composer.lock. Versions <= 7.1.0 are affected; 7.2.0 contains the fix. Check whether your site exposes Special:Ask table output, including request_type=raw, where the sep parameter controls the separator between a cell's values. Authentication is not required to reach the vulnerable output.

Failure mode

sep was inserted verbatim into the HTML that joins a table cell's values. This made it possible to inject HTML through the separator value. The same unsanitised table HTML is produced both for the standard Special:Ask render and for its raw request output (request_type=raw), so the injection was reachable without authentication.

Remediation

• In all non-wiki output modes (HTML, raw request, file), sep is escaped unless it is a safe <br> variant.
• This preserves legitimate line-break separators while blocking markup injection.

Maintenance note

If the table renderer ever gains richer separator semantics, keep the whitelist explicit. Do not expand the allowed HTML surface casually.