An authenticated remote code execution vulnerability exists in GetSimpleCMS version 3.2.1. The application’s upload.php endpoint allows authenticated users to upload arbitrary files without proper validation of MIME types or extensions. By uploading a .pht file containing PHP code, an attacker can bypass blacklist-based restrictions and place executable code within the web root. A crafted request using a polyglot or disguised extension allows the attacker to execute the payload by accessing the file directly via the web server. This vulnerability exists due to the use of a blacklist for filtering file types instead of a whitelist.

GetSimpleCMS Community Edition (CE) versions prior to 3.3.22 (3.3.16 tested) contains a stored cross-site scripting (XSS) vulnerability in the Theme to Components functionality within components.php. User-supplied input provided to the "slug" field of a component is stored without proper output encoding. While other fields are sanitized using safeslashhtml(), the slug parameter is written to XML and later rendered in the administrative interface without sanitation, resulting in persistent execution of arbitrary JavaScript. An authenticated administrator can inject malicious script content that executes whenever the affected Components page is viewed by any authenticated user, enabling session hijacking, unauthorized administrative actions, and persistent compromise of the CMS administrative interface.