CVE-2026-77607: Semantic MediaWiki affected by Special:Ask table `sep` parameter reflected XSS

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.