Haha, well fair enough the crash is bad indeed, good point! This isn't intended behavior though and presumably, it doesn't crash on in cases of this technique being implemented in uninstallers. (a bit of a guess i admit!)

The fact it injects into another process means they can't know if it'll crash or not. You're just one Explorer update away from things changing enough for the hack to crash it.

I guess they could do this more robustly. I.e pause the entire explorer process, save all its state, remotely allocate new memory to inject their code, remotely create a new thread, run only that thread using the injected code, restore all the process' state and finally start it running where it left off. A script would be easier though.

The problem isn’t that the injected thread is racing explorer - indeed, pausing the entirety of explorer to run your uninstaller would probably be strictly more dangerous than what they’re doing - the problem is that the injected thread is using function pointers that do not exist in explorer.exe. Most likely, the reason is that the uninstaller itself has been “detoured” by yet another program to patch calls to certain functions, and it’s copying the detoured addresses instead of the addresses to the real functions.

Both detouring and remote thread injection are supported on Windows, but fall into the category of gray-hat techniques; there are some legitimate uses but quite a lot of illegitimate uses, and using these techniques correctly (without crashing anything!) can be a real challenge.

Agree completely.

I would have assumed (naively?) that they could just copy their uninstaller into a temp folder and run it from there, and just rely on the OS to nuke it in due time, but as a consumer I appreciate the thoroughness of an uninstaller that leaves no trace.

honestly your idea about the tmp dir i think is better than the no trace option. especially given the hacky nature of self deleting stuff. if you have so many uninstallers around that the disk fills up the tmp.dir cleaning would fix it, which is a common first thing to clean when cleaning the filesystem. i like your idea :)

You find the instructions to sweep your floor cumbersome so you reprogram your neighbor's Roomba to come clean your floor. Sure, it may well go back to their house and no harm done, but it's hacky, socially unacceptable, and no matter how hard your broom is to use it's not OK.

The technique could have been made a little more robust by calling GetProcAddress to get the function pointers in Explorer's context, assuming GetProcAddress wasn't itself detoured.