Quote from above link
New protection already active in Firefox 79; will roll out to all Firefox users in the next few weeks.
www.zdnet.com
FIREFOX TO CLEAR COOKIES FOR AD TECH COMPANIES EACH DAY
Mozilla says that going forward, it plans to clear first-party cookies every 24 hours for all known advertisers as a way to prevent redirect tracking. This way, even if advertisers employ redirect tracking, users will have a brand new identity each day, preventing companies from linking previous activity to a unique user profile.
The browser maker said this new protection is included in Enhanced Tracking Protection 2.0, the next iteration of its ETP feature. While currently only active for Firefox 79 users, Mozilla said ETP 2.0 would eventually roll out to all users within the next few weeks.
However, Mozilla says that blocking redirect tracking won't be active for all known ad tech companies.
"Sometimes trackers do more than just track; trackers may also offer services you engage with, such as a search engine or social network,"
Mozilla said, hinting at companies like Google, Microsoft, Facebook, or Twitter.
"If Firefox cleared cookies for these services we'd end up logging you out of your email or social network every day," it said.
For these sites, Mozilla said it would clear cookies every 45 days.
Unquote
24 hrs is a long time. The longer you keep a site open the more cookies will be deposited and the more you'll be tracked.
Should be using Cookie AutoDelete, Site Bleacher or Forget Me Not etc extensions to immediately clear cookies when the tab/window is closed or upon cookie creation. Whitelist only those cookies you want for signing in to sites.
Alternatively, run in Private Browsing Mode or Incoginto Mode to clear cookies upon tab/windows closure but you'll need to sign in each time you visit a site which requires log-in. A bit of a hassle but safer.
Also, use Skip Redirect extension to prevent sites from redirecting.
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