Watcher is a passive-analysis tool for HTTP-based Web applications. It looks for issues related to mashups, user-controlled payloads (potential XSS), cookies, comments, HTTP headers, SSL, Flash, Silverlight, referrer leaks, information disclosure, Unicode, and more. Watcher provides pen-testers hot-spot detection for vulnerabilities, developers quick sanity checks, and auditors PCI compliance auditing. It’s completely safe to use in Cloud computing, shared hosting, and dedicated hosting environments.
Source: https://thehackernews.com/2010/11/watcher-141-latest-version-download.html