Parse Server is vulnerable to authentication bypass via spoofing

Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Parse Server uses the request header x-forwarded-for to determine the client IP address. If Parse Server doesn't run behind a proxy server, then a client can set this header and Parse Server will trust the value of the header. The incorrect client IP address will be used by various features in Parse Server. This allows to circumvent the security mechanism of the Parse Server option masterKeyIps by setting an allowed IP address as the x-forwarded-for header value. This issue has been patched in version 5.4.1. The mechanism to determine the client IP address has been rewritten. The correct IP address determination now requires to set the Parse Server option trustProxy.