I got a popup window saying "Threat blocked. We've blocked UNINSTALLEXCHANGE.PS1 because it was infected with IDP.ALEXA.53", and saying "File path: [my program folder]\AVAST\SETUP\UNINSTALLEXCHANGE.PS1" and "Process: C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe".
There is no file named UNINSTALLEXCHANGE.PS1 in the folder ...\AVAST\SETUP. Was it there before and Avast has moved it? Is UNINSTALLEXCHANGE.PS1 an Avast file? If so, why would it be infected? The only changes I've made to Avast have been to accept their periodic updates.
What does "Process" signify? Did powershell.exe call UNINSTALLEXCHANGE.PS1? While I installed Windows Powershell on my computer a couple of years ago, I've used it rarely if at all, and certainly not recently, and definitely didn't try to access an Avast file, which before now I didn't even know existed.