GoSign Desktop < 2.4.1 - Arbitrary Code Execution via Unsigned Update Manifest
GoSign Desktop versions 2.4.0 and earlier use an unsigned update manifest for distributing application updates. The manifest contains package URLs and SHA-256 hashes but is not digitally signed, so its authenticity relies solely on the underlying TLS channel. In affected versions, TLS certificate validation can be disabled when a proxy is configured, allowing an attacker who can intercept network traffic to supply a malicious update manifest and corresponding package with a matching hash. This can cause the client to download and install a tampered update, resulting in arbitrary code execution with the privileges of the GoSign Desktop user on Windows and macOS, or with elevated privileges on some Linux deployments. A local attacker who can modify proxy settings may also abuse this behavior to escalate privileges by forcing installation of a crafted update.