A HTML injection vulnerability exists in the file upload functionality of Cacti <= 1.2.29. When a file with an invalid format is uploaded, the application reflects the submitted filename back into an error popup without proper sanitization. As a result, attackers can inject arbitrary HTML elements (e.g., <h1>, <b>, <svg>) into the rendered page. NOTE: Multiple third-parties including the maintainer have stated that they cannot reproduce this issue after 1.2.27.