n8n is an open source workflow automation platform. Prior to 1.123.55, 2.25.7, and 2.26.2, three EE endpoints used by the Dynamic Credentials feature accepted any authenticated n8n session without performing per-resource ownership or scope checks on the target workflow or credential. An authenticated user with no project membership or credential sharing relationship could enumerate credential identifiers, names, and types referenced by any private workflow in the instance, initiate an OAuth authorization flow against another user's credential to overwrite its stored tokens with tokens bound to an account they control, or revoke another user's stored credential tokens entirely. Workflows relying on a hijacked credential would subsequently execute under the attacker's OAuth identity, enabling data exfiltration to attacker-controlled external services and persistent takeover of integrations. Token revocation would break affected workflows. This vulnerability is fixed in 1.123.55, 2.25.7, and 2.26.2.