Emlog: Stored XSS via Tag Name in Article Editor

Emlog is an open source website building system. In versions 2.6.29 and prior, tag names in emlog are not HTML-encoded when rendered in the article editor. An attacker can create a tag containing ');alert(document.domain);//. The addslashes() function does not escape HTML entities, so ' is stored as-is. When the browser renders the page, it decodes ' back to a literal single quote before evaluating the JavaScript, breaking out of the string and executing arbitrary code. At time of publication, there are no publicly known patches.