CVE-2026-55744: Cotonti CSRF in PFS allows forced arbitrary file upload

Cotonti 1.0.0 (master branch, commit f43f1fc3) is vulnerable to Cross-Site Request Forgery in the Personal File Storage (PFS) module. In modules/pfs/inc/pfs.main.php, the file upload action ('a=upload') processes uploaded files without calling cot_check_xg() to validate the anti-CSRF token, even though sibling actions such as 'delete' (line 272) do. A remote attacker who lures an authenticated user into visiting a malicious page can force the browser to submit a forged multipart request that uploads arbitrary files into the victim's PFS storage.