One of the things CCleaner cleans is the "session" in various browsers.
Now, I tend to use Chrome or Firefox. I just ran Ccleaner when I had several tabs open in each. After runing CCleaner, no tabs. Does CCleaner wipe these out?
Yes, you discovered your answer yourself. Session wipe will make it so previous tabs are wiped
If you run analyse - for sessions only, look at the detailed results, and maybe right click and go to folder, then you will see that these are mainly log, bak, and other recovery files for that particular browser
So yes these are the files that have info on what tabs were open when the browser last closed (for whatever reason).
As one piece of further clarification, I am running CCleaner free, version 5.32.6129 (64-bit). I just did a cleanup, and I had my Microsoft Edge "Session" option checked. I now lost my saved tabs, a new feature in Windows 10 version 1703. Is this saved in the MS Edge session even if you exit the program? I have it turned off in the background apps, and I have restart my computer and the tabs save in the top-left corner to be recovered later.
I don't think anyone but the developers at Microsoft could answer that one.
(And they would probably struggle to know what their co-worker at the next workstation has just changed in the Edge basecode).
Edge is a work in progress, and they keep changing things.
Which is one reason why third party cleaners, AV's etc. have problems keeping up with just what MS have changed in Edge from month to month.
(Or week to week if you are on the insider rings).