Start Firefox in Safe Mode to check if one of the extensions (Firefox menu button/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem.

• Switch to the DEFAULT theme: Firefox menu button/Tools > Add-ons > Appearance
• Do NOT click the Reset button on the Safe Mode start window

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

Just retested with FF 43.0 and followed the instructions. Only DEFAULT theme available. Never used something different. Safe Mode did not solve the issue.

Simple to reproduce: open FF and open private window. Press CMD-F. Enter a find phrase. Close FF. Open FF. Press CMD-F. See find phrase from previous private session.

Hmm, it could be a Mac thing.

After using find in a private window, could you paste into the search bar and into another application to see whether the find text is on the clipboard?

Similarly, could you copy some other text before quitting down and restarting Firefox to see whether that shows up in the find bar?

Did you quit the Firefox application or merely closed the window(s)?

In case of the latter then Firefox will still be running. If you close the Firefox application then this shouldn't happen.

• "3-bar" menu button > Exit (Power button)
• Mac: Firefox > Quit Firefox

@jscher2000: just tried the clipboard testing on a different mac which exhibits the same issue.

The find term entered and shown is completely decoupled from the clipboard. It does not influence clipboard contents, neither while FF is running nor afterwards. Also the clipboard contents to not influence the find term, neither the contents in there before FF is started nor while FF is running.

Just to make sure we are talking about the same thing: you wrote "search bar" which in my current terminology is the input field at the upper right top of the screen beneath the address bar. I wrote "find term" which in my current terminology is the input field at the lower left bottom of the screen and only appears after pressing CMD-F aka Menu "Edit" -> "Find" in page.

@cor-el: I usually close all windows first pressing the "red" close button at the upper- and leftmost part of the windows. Then I *always* use CMD-Q to finally quit the FF application. The dot at the FF icon in the dock then disappears to indicate application shutdown.