Opener Detector is a free browser extension developed by Harry Cutts. It is designed to check for window.opener vulnerabilities as you browse the internet. This simple yet powerful tool helps identify potential vulnerabilities and provides a warning page in the vulnerable tab, allowing you to report or fix the issue.

With Opener Detector, you have the ability to add individual pages or entire domains to an ignore list. By default, vulnerabilities between pages of the same origin are not reported, but this setting can be adjusted to suit your needs.

Window.opener vulnerabilities can be a serious security risk, as they allow web pages to control the tab that opened them. Opener Detector helps mitigate this risk by alerting you to potential vulnerabilities and providing guidance on how to fix them. By adding the "rel=noopener" attribute to your links, you can easily prevent these vulnerabilities. For more information, you can refer to Mathias Bynens' article on the topic.

Opener Detector is available as a Chrome extension and can be downloaded from the Chrome Web Store. The source code is also available on GitHub under the 3-clause BSD license, welcoming contributions from the community. Please use this extension responsibly and disclose any vulnerabilities you find or fix them yourself. Stay safe and keep your hat white.