The MediaWiki Collection extension contains a flaw that allows arbitrary URL redirection when users access the Special:Book page. The flaw originates from accepting a redirect target parameter without proper validation, leading to an open redirect (CWE‑601). An attacker can funnel users to untrusted sites, facilitating phishing or social engineering attacks that undermine trust in the originating site. Based on the description, it is inferred that the redirect target can be supplied via a query parameter on the Special:Book endpoint.

Vulnerable versions are MediaWiki Collection extension 1.43.10, 1.45.5, and 1.46.0 and earlier. These are used by the Wikimedia Foundation on its systems. Sites hosting the Collection extension and providing the Special:Book endpoint, before these patch releases, are susceptible.

With a CVSS score of 6.1 and an EPSS score of less than 1%, this open redirect is moderate in severity yet still exploitable via a simple crafted link. The vulnerability is not listed in the CISA KEV catalog. An attacker can redirect users to untrusted sites by passing the target URL in a query parameter on the Special:Book page. The exploit requires only a malicious URL and a user click, making it a feasible phishing vector. Until a patch is deployed, monitoring and user education are advised.