Sparkle's AppInstaller post-stage-1 XPC listener accepts unvalidated connections, allowing spoofed appcast item data injection

Summary AppInstaller post-stage-1 XPC listener accepts unvalidated connections, allowing spoofed appcast item data injection. Details Autoupdate/AppInstaller.m's shouldAcceptNewConnection: only enforces SUCodeSigningVerifier validateConnection: before stage 1 completes. After...