GHSA-45v3-38pc-874v

This issue was identified during Quarkslab's audit of the timestamp feature.

### Summary During the timestamp signature generation, the revocation status of the certificate(s) used to generate the timestamp signature was not verified.

### Details During timestamp signature generation, notation-go did not check the revocation status of the certificate chain used by the TSA. This oversight creates a vulnerability that could be exploited through a Man-in-The-Middle attack. An attacker could potentially use a compromised, intermediate, or revoked leaf certificate to generate a malicious countersignature, which would then be accepted and stored by `notation`.

### Impact This could lead to denial of service scenarios, particularly in CI/CD environments during signature verification processes because timestamp signature would fail due to the presence of a revoked certificate(s) potentially disrupting operations.