KNOXSS Community Edition is a FREE standalone version of the KNOXSS browser add-on, designed to identify the primary XSS (Cross-Site Scripting) cases listed here.
In the current version (beta 0.2.0), it can detect all the XSS cases for GET and POST requests. Simply open one of the testing URLs and click on the add-on's icon in your Firefox browser.
The main advantages are HIGH SPEED and GOOD EFFICIENCY in finding covered cases in regular scenarios (exact reflection of input in response).
However, it is highly susceptible to both false positives and false negatives since it works by parsing the source code rather than detecting actual JavaScript execution, unlike the main KNOXSS.
