LinuxServer.io heimdall 2.6.3-ls307 contains a vulnerability in how it handles user-supplied HTTP headers, specifically `X-Forwarded-Host` and `Referer`. An unauthenticated remote attacker can manipulate these headers to perform Host Header Injection and Open Redirect attacks. This allows the loading of external resources from attacker-controlled domains and unintended redirection of users, potentially enabling phishing, UI redress, and session theft. The vulnerability exists due to insufficient validation and trust of untrusted input, affecting the integrity and trustworthiness of the application.

LinuxServer.io Heimdall before 2.7.3 allows XSS via the q parameter.

An issue in Linux Server Heimdall v.2.6.1 allows a remote attacker to execute arbitrary code via a crafted script to the Add new application.

LinuxServer.io Heimdall before 2.5.7 does not prevent use of icons that have non-image data such as the "<?php ?>" substring.

Heimdall Application Dashboard through 2.5.4 allows reflected and stored XSS via "Application name" to the "Add application" page. The stored XSS will be triggered in the "Application list" page.