Probo is a self-hostable governance, risk, and compliance (GRC) platform built for engineering and security teams. Prior to version 0.224.0, the public Trust Center GraphQL API exposes acceptElectronicSignature and recordSigningEvent, both gated only by @authentication(required: PRESENT) @sessionOnly — any self-provisioned trust center identity can call them. The underlying esign.Service.AcceptSignature and esign.Service.recordEvent build the tenant scope from the client-supplied signatureId GID (coredata.NewScopeFromObjectID(req.SignatureID)) and load the signature by that GID. At no point do they verify that the signature belongs to the caller or that the caller's email matches the signature's SignerEmail. As a result, any authenticated trust-center visitor who possesses another visitor's signature GID can: (1) complete that visitor's NDA signature — overwriting signer name/IP/UA with attacker data and setting status to Accepted, which triggers the sealing worker to generate a completion certificate; (2) inject arbitrary audit-trail events into any signature's log. Both attacks defeat the non-repudiation and integrity guarantees of the e-signature system. This issue has been patched in version 0.224.0.