Logging in through CyberArk Identity dies at the callback with "Unsupported {'app_id'} in header" and the user sees "The email or password provided is incorrect". Any provider that puts a vendor-specific parameter in the ID token header hits this; CAS was already patched by name, CyberArk is the next one.
Authlib 1.7 verifies ID tokens with joserfc, which rejects header parameters it does not recognise. The old fix registered `client_id` so CAS would work, which only ever fixes one provider at a time. This turns off the unknown-header rejection instead, so any private header parameter is ignored rather than fatal. Signature verification, the algorithm allowlist, `crit` handling and value validation of registered headers all still run, so nothing that actually protects the token is relaxed.
Fixes#28062
Classic298
5462c02af0