Comment 6 for bug 1861913

User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:73.0) Gecko/20100101 Firefox/73.0

Steps to reproduce:

Enabled Strict tracking protection and, after several weeks of using Firefox, launched Firefox one day and the bug occurred. I have not been able to reliably reproduce it, though once in the buggy state, it reproduces on every launch.

I've experienced this on (Ubuntu's version of) 72.x and 73.x, as well as back in August on what would probably have been 68.x (but I didn't make a note).

Actual results:

No tabs would display any content. I restored my tabs, so this included pins, regular sites, and extension dialogs. Further to that, Firefox menus also wouldn't display; either via right-click on tabs, or via the "hamburger" menu in the top-right. (I could still close tabs via Ctrl-W for non-pinned tabs, or via middle-click for pinned tabs.)

favicons were displayed correctly, and I confirmed that the pages were actually being fetched from the remote sites because I typed the address for a page I know redirects and the redirect happened (specifically, "!g foo" in my address bar caused DuckDuckGo to redirect me to Google).

Restarting the browser did not fix this. Closing all of my tabs and restarting the browser did not fix this. Closing all of my tabs and restarting the browser, however, _did_ allow the Firefox menus to render (provided I didn't try to open any web pages before using them), which allowed me to switch "Enhanced Tracking Protection" from Strict to Standard, fixing the problem (on browser restart).

I also noticed that at least part of the problem appears to apply only per-window: if I opened a new window then menus would render in that window (until I opened a web page).

I have been able to re-enable Strict mode on the first launch after switching away from it, and the browser continues to function normally.

Expected results:

Firefox should have behaved as it always does, displaying site content.