A file upload vulnerability was discovered in CS Cart 4.18.3, allows attackers to execute arbitrary code. CS Cart 4.18.3 allows unrestricted upload of HTML files, which are rendered directly in the browser when accessed. This allows an attacker to upload a crafted HTML file containing malicious content, such as a fake login form for credential harvesting or scripts for Cross-Site Scripting (XSS) attacks. Since the content is served from a trusted domain, it significantly increases the likelihood of successful phishing or script execution against other users.