CVE-2024-21641: Flarum's logout Route allows open redirects

January 5, 2024 (updated January 17, 2025)

The Flarum /logout route includes a redirect parameter that allows any third party to redirect users from a (trusted) domain of the Flarum installation to redirect to any link. Sample: example.com/logout?return=https://google.com. For logged-in users, the logout must be confirmed. Guests are immediately redirected. This could be used by spammers to redirect to a web address using a trusted domain of a running Flarum installation.

Some ecosystem extensions modifying the logout route have already been affected. Sample: https://discuss.flarum.org/d/22229-premium-wordpress-integration/526

References

github.com/advisories/GHSA-733r-8xcp-w9mr
github.com/flarum/flarum-core/commit/ee8b3b4ad1413a2b0971fdd9e40f812d2a3a9d3a
github.com/flarum/framework/commit/7d70328471cf3091d92d95c382d277aec7996176
github.com/flarum/framework/security/advisories/GHSA-733r-8xcp-w9mr
nvd.nist.gov/vuln/detail/CVE-2024-21641

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