Mysterious dialog


I was listening to a video via VLC in full screen mode. TimeMachine has been doing a backup for some time. I saw some dialog box show up for a few seconds... disappear... show up again for a few seconds, and then disappear again. I think it said "Mounting base.dmg" but it was fairly quick.

/var/log/system.log and all the other logs do not show anything. I thought maybe it was actually in the video so I backed up the video and played through the section again -- no message.

I have some gaming software, Adobe software, etc. I try to set all those so they do not automatically update but I'm not 100% sure all of them are set that way.

Any suggestions on what to do?

Thank you,
It's hard to recommend anything, when you don't know what was making the notification pop up.
If that was really "mounting base.dmg", then that doesn't really sound like any automatic app update.

Could be that something could have installed (and not an update of anything that you already have)...
Were you streaming a video over the internet? or watching a local video that you had previously downloaded, or copied from somewhere else?
Sometimes a dodgy video source will offer you a "better" or "new" video player, which turns out to be an app that you don't need (or don't want)
That can also be a possibility of adware of some kind.
This may be a good opportunity to test THAT theory by running a scan with Malwarebytes, if you already keep that good utility.
If you do not have Malwarebytes, you can get it here. It's free to use. It does have a "paid" mode, and it uses that mode the first time you install it, which gives you 30 days of use. You can then continue to use it for free, and it reverts to a free mode, which basically means that you can do a manual scan when you feel like it. It doesn't interfere with your system in any way --- the free mode is not a full-time scan. It WILL remove any threat that it might find. Pretty good stuff for the Mac.