SPIP Unauthenticated RCE via porte_plume Plugin

This module exploits a Remote Code Execution vulnerability in SPIP versions up to and including 4.2.12.
The vulnerability occurs in SPIP's templating system where it incorrectly handles user-supplied input,
allowing an attacker to inject and execute arbitrary PHP code. This can be achieved by crafting a
payload manipulating the templating data processed by the `echappe_retour()` function, invoking
`traitements_previsu_php_modeles_eval()`, which contains an `eval()` call.