bugs found in Avast

Avast Free Antivirus / Premium Security
1

I was running a boot scan on a 64-bit Windows 7 PC, using the latest free version of Avast, and I found what seem to be a pair of serious bugs:

  1. when I hit the up-arrow on my keyboard during the scan, hoping it would let me backtrack through the onscreen report, Avast interpreted this as me pressing 8, which told it to ignore all viruses and worms. This was me pressing the arrow key, not the up-arrow on the num pad.

  2. Since a scan where all problems are ignored is useless, I hit escape to cancel the scan and reboot the machine. The scan canceled, but when the machine rebooted and I logged into Windows, all I got was a black screen with a mouse cursor. I can move the mouse cursor around, and if I hit ctrl-shift-esc, I get a task manager I can interact with, but there is no start menu, no task bar, and no right-click functionality on the desktop.

If I try to log off or shut down, Windows tells me that a process called TaskMgr is doing something and is thus blocking the shutdown. When I say “force shutdown”, it acts like it is doing that, but actually just sits there like a brick, spinning the hard drive until I cut the power and start over.

This is the second time I’ve run into this problem after interrupting an Avast boot scan. The first time, I tried rebooting several times afterward, but kept getting the black screen until I finally went into safe mode and uninstalled Avast. This is a pretty serious problem.

-Z

2

I will filter the arrow keys so that they don’t behave like the num-pad arrows.

As for the second thing, however… I can’t really imagine how the boot-time scanner could cause this. I mean, the boot-time scanner is just an ordinary application - which is started, runs, and exits after it’s done - and the boot continues after that. No staying on background or anything like that (and certainly no changing anything permanently for the next boot).
If any file had been detected and removed during the scan, then sure, it might have corrupted something - but if it wasn’t the case, my guess would be some kind of timing issue (starting of the boot-time scan application changes the order of the following modules being loaded by Windows, which somehow causes the described conflict - with or without anything from avast! involved).
So without having this particular behavior reproduced on a local machine (which it certainly doesn’t, the scanner and the scan interruption work just fine), there’s very little I can do.

If you were willing to create and upload a full memory dump taken at the moment the “black screen” problem is reproduced, it might tell us more about what’s going on there. The description on how to invoke the dump is here (meant for PS/2 keyboard; for USB keyboards the registry key is different).