I have set Firefox to not automatically restore the previous session on launch. That is, "Open previous windows and tabs" is unchecked in the Startupsettings. Most of the time it does not do so, however the previous session will get erroneously auto-restored in the folowing circumstances. Open a few tabs in a normal Firefox window. Fully quit Firefox (via, for example, pressing ctrl+shift+Q). Open a private window first. Open a normal window second. What should happen is that the new normal window contains just a single new tab. What actually happens is that the tabs that were open in the previous session get auto-restored in this normal window. To sum up, there is no auto-session restore if Firefox is launched with a normal window first. There is auto-session restore if Firefox is launched with a private window first, and then a normal window is opened second. Is this a known issue, and are there any known fixes to prevent the auto-session restore in the latter case also?