Possible installation issues in Safari on OS X El Capitan

We received some users' report on problems with installing FastestTube for Safari on OS X El Capitan. If you have also experienced any problems with installation, please read the explanation and possible solutions below.

Problem

A warning message appears after double clicking the plugin icon when using OS X El Capitan. The plugin doesn't get installed after clicking the Trust button.

The main cause of this problem is a deliberate change by Apple to address CVE‑2015‑5943. The reason is that a malicious application may programmatically control keychain access prompts. Since MacOS X 10.11.1, to solve this issue, Apple has disabled keychain dialogs if there are some synthetic/programmatic interactions with them. (The confirmation dialog with Trust button is exactly the keychain prompt). But there are many legitimate software that performs such an interactions. In this case, if such a software is active, you will be not able to use keychain prompts because of security mechanism described above.

Software that causes the problem, according to users' reports and our investigation:

• Flycut (Clipboard manager)
• MagicPrefs
• Karabiner
• Punto Switcher
• Seil
• SmoothMouse
• Alfred
• TextExpander
• and other which use methods of interactions with windows they not own.

So, we observe exactly the same behavior while such software is installed and runned - nothing happenes after clicking Trust button (MacOS shows the dialog, third-party software performs some programmatic interaction with it, then MacOS block this dialog because of this interactions). Unfortunately, there is no simple way to determine which exactly software that leads to the problem.

We can suggest two possible solutions.

Solution 1

Find the culpable application and add it to the Approved Apps list:

• Unload/quit all the potentially suspicious software.
• Try to run it one by one until the problem repeats.
• Define the software that causes the problem.
• Go to System Preferences Security & Privacy Accessibility, then add this software to the Approved Apps list:
• If it doesn't help, try to quit this software manually before installing the extensions.

Solution 2

The other confirmed solution is to install FastestTube via the Safe mode. To install in the Safe mode:

• Choose Apple menu Shut Down.
• After your Mac shuts down, wait 10 seconds, then press the power button.
• Immediately after you hear the startup tone, hold down the Shift ⇑ key.
• You should press the Shift ⇑ key as soon as possible after you hear the startup tone, but not before.
• Release the Shift ⇑ key when you see the gray Apple logo and progress indicator.
• Install FastestTube as usual. The confirmation dialog should work fine in Safe mode.
• To leave safe mode, restart your Mac again, but don’t hold down any keys during startup.