Edit: the linked issue is regard "instart" which seems to exploit a Chromium flaw that allows it to disguise third-party cookies as first-party, preventing filtering based on that categorization alone.
It seems it's getting harder to rely on browsers working how they were originally intended.
Instart is a MITM service like Cloudflare. It more or less partners with adproviders to serve thirdparty requests through a proxy on the first party domain.
https://github.com/jspenguin2017/uBlockProtector/issues/95
Edit: the linked issue is regard "instart" which seems to exploit a Chromium flaw that allows it to disguise third-party cookies as first-party, preventing filtering based on that categorization alone.
It seems it's getting harder to rely on browsers working how they were originally intended.