Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to versions 8.6.10 and 9.5.0-alpha.11, the Google, Apple, and Facebook authentication adapters use JWT verification to validate identity tokens. When the adapter's audience configuration option is not set (clientId for Google/Apple, appIds for Facebook), JWT verification silently skips audience claim validation. This allows an attacker to use a validly signed JWT issued for a different application to authenticate as any user on the target Parse Server. This issue has been patched in versions 8.6.10 and 9.5.0-alpha.11.