Callback-url-file-3a-2f-2f-2fproc-2fself-2fenviron May 2026

callback-url-file-3A-2F-2F-2Fproc-2Fself-2Fenviron After decoding, the server executes:

It is important to clarify at the outset that the string you provided— callback-url-file-3A-2F-2F-2Fproc-2Fself-2Fenviron —is a URL-encoded representation of a very specific and dangerous file path: callback-url-file-3A-2F-2F-2Fproc-2Fself-2Fenviron

Thus, the full decoded path is:

file_get_contents("file:///proc/self/environ") The server reads its own environment memory and returns it in the HTTP response – exposing every secret. patch the vulnerable endpoint

https://example.com/process-payment?callback_url=https://trusted-partner.com/confirm If the code does something like: callback-url-file-3A-2F-2F-2Fproc-2Fself-2Fenviron

Investigate immediately, patch the vulnerable endpoint, and rotate all secrets that may have lived in /proc/self/environ at the time of the request.