This only applies to browsing where the user's cache is present, yes?
At least in Firefox 85.0.1 Desktop and 85.1.1 Android (when I tested) clearing the cache also nukes the favicons as well.
Also, I get different hashes when I test on demo.supercookie.me after clearing my cache on mobile, and also across Private windows on desktop.
The statement "[...] even in the browser's incognito mode and is not cleared by flushing the cache, closing the browser [...]" is misleading, at least where Firefox[0] is concerned.
Tested on Firefox 85.0 on Linux mint. The id is different across a normal window and a private window.
Also tried using a new profile using `about:profiles` and again the id was different.
At least in Firefox 85.0.1 Desktop and 85.1.1 Android (when I tested) clearing the cache also nukes the favicons as well.
Also, I get different hashes when I test on demo.supercookie.me after clearing my cache on mobile, and also across Private windows on desktop.
The statement "[...] even in the browser's incognito mode and is not cleared by flushing the cache, closing the browser [...]" is misleading, at least where Firefox[0] is concerned.
[0] https://blog.mozilla.org/security/2021/01/26/supercookie-pro...