This extension is useful only on a predetermined set of sites, it won't do anything outside that specific set of sites. The following link shows on which sites uBO-Extra is useful:
### Release notes
An (optional) companion extension to uBlock Origin: to gain ability to foil early hostile anti-user mechanisms working around content blockers.
Instart Logic's technology used to disguise third-party network requests as first-party network requests, INCLUDING the writing/reading of third-party cookies. I consider this to be extremely hostile to users, even those NOT using a content blocker, as it allows third-party servers to read/write cookies even if a user chose to block 3rd-party cookies.
The company behind the technology understand how hostile its technology is to users, and thus tries to hide what is being done by making it difficult to investigate by detecting whether the browser's developer console is opened, and when it detects it is opened, it ceases completely to make use of the obfuscation mechanism. The developer console-detecting code works only for Chromium-based browsers however, and therefore the obfuscation technology is not used when using Firefox (a different web page is served for Firefox).
The extension has no interactive UI, just an icon in the toolbar to remind it's enabled.
Your browser should allow you to hide the icon if it annoys you. Use uBlock Origin's logger if you want to see and possibly filter WebSocket connections made visible by uBO-Extra.