User Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:47.0) Gecko/20100101 Firefox/47.0 Build ID: 20160623154057 Firefox for Android Steps to reproduce: Firefox 48.0 on Android 6.0 running 3.10.84-g7601311 lge@android-build Settings --> "Clear private data on exit" (Checked) -- All subitems checked. Go browse the web. I go to news.google.com or m.facebook.com when I'm at lunch. Explicitly select 'Quit'. Put away phone. Go do something else. Or not. Open firefox browser again, the pages of sites I've visited and articles are now prominently displayed on Top Sites. Frequency of problem: 90%. 10% of the time it actually clears. It's been getting worse it seems. Workaround: Explicitly go to Settings --> Clear private data --> (All boxes are already checked for me) --> Press 'CLEAR DATA' Actual results: The pages of sites I've visited and articles are now prominently displayed on Top Sites. Expected results: All the data should've been cleared on quit. No trace of what I've browsed should be visible when browser is started again. Top Sites should not show the screenshots of pages I've looked at.

I did a search before opening this bug, and I didn't find anything else open currently. However, I did find this closed question from last year: https://support.mozilla.org/en-US/questions/1042872 And it was claimed to be fixed in 39.0. Maybe some old code was re-introduced?