GHSA-w6c6-c85g-mmv6 Cosign's verify-blob-attestation reports false positive when payload parsing fails

• Go github.com/sigstore/cosign: >= 3.0.0, < 3.0.6 → fixed in 3.0.6 • Go github.com/sigstore/cosign: < 2.6.3 → fixed in 2.6.3

Description `cosign verify-blob-attestation` may erroneously report a "Verified OK" result for attestations with malformed payloads or mismatched predicate types. For old-format bundles and detached signatures, this was due to a logic flaw in the error handling of the predicate type validation. For new-format bundles, the predicate type validation was bypassed completely. Impact When `cosign verify-blob-attestation` is used without `--check-claims` set to `true`, an attestation that has a valid signature but a malformed or unparsable payload would be incorrectly validated. Additionally, systems relying on `--type ` to reject attestations with mismatched types would be lead to trust the unexpected attestation type. Patches v3.0.6, v2.6.3 Workarounds Always set `--check-claims=true` for attestation verification.