Mojolicious is a real-time web framework for Perl. Prior to 9.48, the Mojolicious CSRF helpers csrf_field, csrf_token, and csrf_protect reuse an unchanged per-session token in rendered HTML. When response compression is enabled and attacker-influenced content is reflected in the same response, an unauthenticated attacker who can induce many victim requests and observe response sizes can use a BREACH compression side channel to recover the token and forge cross-site requests. API-only deployments that never render the token in HTML are not affected. This issue is fixed in version 9.48.