In CMS Made Simple 2.2.3.1, the is_file_acceptable function in modules/FileManager/action.upload.php only blocks file extensions that begin or end with a "php" substring, which allows remote attackers to bypass intended access restrictions or trigger XSS via other extensions, as demonstrated by .phtml, .pht, .html, or .svg.
Severity
CVSS 3.1
5.4 medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
EPSS
0.9% chance of exploitation in the next 30 days; higher than 58% of CVEs (scores of 2026-10-31)