CVE-2026-77609

#### Failure mode `Special:URIResolver` resolves its user-controlled subpage to a MediaWiki title and issues an HTTP 303 redirect to `$title->getFullURL()` without validating the resolved target. A crafted subpage can make that target point off-host: an interwiki prefix redirects to the foreign wiki (for example `Special:URIResolver/mw-3AFoo`, which decodes to `mw:Foo`, redirects to `https://www.mediawiki.org/wiki/Foo`), and where the resolved URL carries an authority the target can even embed `user:pass@host` credentials. The result is an open redirect to an attacker-influenced host, usable for phishing from a trusted wiki URL. #### Remediation - The resolved target URL is parsed and compared against the current host at the redirect sink. - The redirect is rejected (bad-title error page) when a user or pass component is present, or when the host does not match the current host. #### Maintenance note Redirect code must validate the final target URL, not just the input path. Host comparison belongs at the redirect sink: each sink (special page, entry point) must validate its own target rather than relying on upstream normalisation.