Coder's workspace app upsert allows cross-workspace agent rebinding via user-controlled app ID

Coder allows organizations to provision remote development environments via Terraform. Prior to versions 2.29.7, 2.32.7, 2.33.8, and 2.34.2, UpsertWorkspaceApp overwrites an existing app's agent_id on a primary-key conflict and insertAgentApp accepts the app ID from the provisioner's CompleteJob payload without verifying it belongs to the workspace being built. CompleteJob runs under dbauthz.AsProvisionerd so the authorization layer does not block the cross-workspace upsert. Exploitation requires elevated access as a template author or external provisioner operator. The fix in versions 2.29.7, 2.32.7, 2.33.8, and 2.34.2 verifies that any existing workspace_apps row matching the supplied ID belongs to the workspace being built and rejects cross-workspace agent reassignment. No known workarounds are available.