n8n before 1.123.80, 2.39.6, and 2.40.1 Information Disclosure via Credential Test Endpoint

n8n versions before 1.123.80, from 2.0.0 before 2.39.6, and from 2.40.0 before 2.40.1 contain an authorization bypass vulnerability in the credential test endpoint that resolves project-scoped variables without validating caller access. Attackers can specify an arbitrary project ID in the request body to interpolate sensitive variables into credential test requests sent to attacker-controlled hosts for exfiltration.