extension simply unblocks CORS limitation when it is enabled. Basically, the extension inserts two new headers to every web requests: 'access-control-allow-origin' is set to '*' which allows access to the web request from all origins and 'access-control-allow-methods' header is set to allow 'GET', 'PUT', 'POST', 'DELETE', 'HEAD', 'OPTIONS', 'PATCH' methods which allow XMLHttpRequest for these methods. You can ask the extension to not overwrite these headers if they do already exist. Also, you can limit the allowed methods from right-click context menu over the toolbar button. Note that this extension is disabled by default to prevent unintended unblocking. To enable it, click the toolbar button once. When the extension is enabled, the toolbar button is colorful.