In Perfex Crm < 3.2.1, an authenticated attacker can send a crafted HTTP POST request to the affected upload_sales_file endpoint. By providing malicious input in the rel_id parameter, combined with improper input validation, the attacker can bypass restrictions and upload arbitrary files to directories of their choice, potentially leading to remote code execution or server compromise.
The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.