[1]: https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/Web...
[2]: https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/Web...
Firefox isn't susceptible to that, because that's not how Firefox and addons.mozilla.org work. Chrome, as it turns out, isn't susceptible to it, either, because that's also not how Chrome and the Chrome Web Store work. (And that's not what LinkedIn's fingerprinting technique does.)
(Those randomized IDs for content-accessible resources, however, do explain why the technique that LinkedIn actually uses is is a non-starter for Firefox.)
Edit: Can't find much documentation on exactly how the anti-fingerprinting works, but this page implies that the browser blocks extension detection: https://support.mozilla.org/en-US/kb/trackers-and-scripts-fi...