OS X Yosemite: Allow accessibility apps to access your Mac
When a third-party app tries to access and control your Mac through accessibility features, an alert informs you, and you must specifically grant the app access to your Mac in Security & Privacy preferences.
If you’re familiar with an app, you can authorize it by clicking Open System Preferences in the alert, then selecting the checkbox 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.
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, then select the app’s checkbox. To remove an app’s access to your Mac, deselect the checkbox. You can also drag an app into the pane to add it yourself, then select the app’s checkbox.
If you enabled access to assistive devices in OS X Mountain Lion or earlier, the setting isn’t maintained in OS X Mavericks or later; you must grant apps access in Security & Privacy preferences.