It is happening on different sites : YouTube, Twitter, Gmail. I didn't track how long it takes, but roughly once a week the sites silently log me out. YouTube most often. Today it was Twitter.
On YouTube, after a 'shadow logout,' if I click the Sign In button, YouTube doesn't ask for credentials but reloads the page and shows me the home page i.e., it authorizes me silently.
To do that.
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