Question
MacOS Catalina – System Preferences -> Security & Privacy -> Privacy -> Accessibility
What does granting 'control (of) your computer' include?
The following question from 2013 provides some very broad information:
What does Security & Privacy/Accessibility enable?
but I would greatly appreciate any more specifics that people can provide.
Background
Even if I trust an app now (no mean feat), there is always the possibility that it could suffer a supply-chain attack in the future.
I would like to understand more about the damage that an app could do if I grant it access to my Mac.
Research
I found the following page in the Apple Developer documentation:
https://developer.apple.com/library/archive/documentation/LanguagesUtilities/Conceptual/MacAutomationScriptingGuide/AutomatetheUserInterface.html
It seems like one example of 'control' could be for an app to instruct Safari to open a particular (malicious) website?
Best Answer
As you saw in your research, the accessibility api allows one app to control other apps on your computer, in much the same way you do with your mouse and keyboard. These apps can resize windows, click buttons, type words, copy and paste, etc.
If you want an app to be able to do any of these things for you, you will need to grant access to the accessibility api (ie, "allow it to control your computer"). If you'd rather it not have that ability, or if there's no reason for it to have that ability, deny access.
Zoom is an example of an app that I do not allow to use the accessibility API. It asks, but I don't know why, because there's no reason Zoom should ever need to click or type in my place.