Unrestricted file upload

Vtiger CRM through 8.4.0 contains an authenticated remote code execution vulnerability in the admin module import feature that allows administrator-level attackers to upload arbitrary PHP files by submitting a crafted zip archive through the ModuleManager import function, which extracts contents directly into the modules/ directory under the web root without validating file types beyond the manifest.xml descriptor. Attackers can place executable PHP files in the modules/ directory that become directly accessible via HTTP, bypassing Vtiger's authentication and authorization layer entirely since Apache resolves the path and invokes the PHP interpreter before the application routing layer is involved, resulting in a persistent web shell independent of the originating session.