Server-Side Request Forgery (SSRF) vulnerability exists in the URL processing functionality of PHProxy version 1.1.1 and prior. The input validation for the _proxurl parameter can be bypassed, allowing a remote, unauthenticated attacker to submit a specially crafted URL
The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.