FreeScout is a free, self-hosted help desk and shared mailbox. A stored HTML Injection vulnerability has been identified in the Email Receival Module of the Freescout Application. The vulnerability allows attackers to inject malicious HTML content into emails sent to the application's mailbox.

This vulnerability arises from improper handling of HTML content within incoming emails, allowing attackers to embed malicious HTML code in the context of the application's domain. Unauthenticated attackers can exploit this vulnerability to inject malicious HTML content into emails. This could lead to various attacks such as form hijacking, application defacement, or data exfiltration via CSS injection.

Although unauthenticated attackers are limited to HTML injection, the consequences can still be severe. Version 1.8.139 implements strict input validation and sanitization mechanisms to ensure that any HTML content received via emails is properly sanitized to prevent malicious HTML injections.