The cBioPortal for Cancer Genomics provides visualization, analysis, and download of large-scale cancer genomics data sets. When running a publicly exposed proxy endpoint without authentication, cBioPortal could allow someone to perform a Server Side Request Forgery (SSRF) attack. Logged in users could do the same on private instances. A fix has been released in version 6.0.12. As a workaround, one might be able to disable /proxy endpoint entirely via, for example, nginx.
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.