Allow accessibility apps to access your Mac
When a third-party app tries to access and control your Mac through accessibility features, you receive an alert, and you must specifically grant the app access to your Mac in Security & Privacy preferences.
If you’re familiar with an app, you can authorise it by clicking Open System Preferences in the alert, then selecting the tickbox for the app in the Privacy pane. If you’re unfamiliar with an app or you don’t want to give it access to your Mac at that time, click Deny in the alert.
Be cautious and grant access only to apps that you know and trust. If you give apps access to your Mac, you also give them access to your contact, calendar and other information, and are subject to their terms and privacy policies and not the Apple Privacy Policy. Be sure to review an app’s terms and privacy policy to understand how it treats and uses your information.
Denied apps are listed in the Accessibility section of the Privacy pane. If you later decide to give a denied app access to your Mac, choose Apple menu 
> System Preferences, click Privacy, click Accessibility, then select the app’s tickbox. To remove an app’s access to your Mac, deselect the tickbox. You can also drag an app into the pane to add it yourself, then select the app’s tickbox.