RFC 6960 Online Certificate Status Protocol endpoint. This URL accepts:
Content-Type: application/ocsp-request and a DER-encoded OCSPRequest in the body./<base64(OCSPRequest)> per RFC 6960 §A.1.1.Browsers, RP libraries, and Adobe Reader fetch this automatically when validating a certificate’s revocation status — no manual action is needed.
Related: CRL distribution point.