sealed-secrets /v1/rotate can widen sealing scope to cluster-wide via attacker-controlled template annotations

Bitnami Sealed Secrets is vulnerable to a scope-widening attack during
the secret rotation (/v1/rotate) flow. The rotation handler derives the
sealing scope for the newly encrypted output from untrusted
spec.template.metadata.annotations present in the input SealedSecret.
By submitting a victim SealedSecret to the rotate endpoint with the
annotation sealedsecrets.bitnami.com/cluster-wide=true injected into the
template metadata, a remote attacker can obtain a rotated version of the
secret that is cluster-wide. This bypasses original "strict" or
"namespace-wide" constraints, allowing the attacker to retarget and unseal
the secret in any namespace or under any name to recover the plaintext
credentials.