Avast High Sierra System Extension Blocked

Hi,

Safari 11 is the currently-available version of Apple’s desktop browser and was released in September 2017 as part of macOS High Sierra, the latest version of Apple’s Mac operating system. Safari is no longer available as a standalone download and is instead included as a part of the OS. However, at the time this report was published (late June 2019), the older versions (e.g. High Sierra) exhibiting the same flaw had still not been patched. APPLE-SA-2019-5-13-2 DesktopServices Available for: macOS Mojave 10.14.4 Impact: A malicious application may bypass Gatekeeper checks Description: This issue was addressed with improved checks. It protects your identity, ensures your privacy, and secures your files, folders, and computer. Avast comes in two versions: Avast Security for Mac is a free download. Avast Premium Security is licensed for 1, 2, or 3 years for with single or multi-device options (up to 10). The premium version offers a 60-day free trial and a 30-day money-back.


Today I couldn't run a Windows 10 VM on a Mac Host, nor update my VirtualBox 6.x to version 6.1.14. In both cases I receive an error saying that the 'Kernel driver not installed (rc=-1908)'. I don't remember to have updated High Sierra since the last time I run VirtualBox, nor changed anything in my system.
By searching in the forum, I see that this may be caused by the VB kernel extensions being blocked by High Sierra. EtreCheck says, actually, that all the VB extension are not loaded:
[Not Loaded] VBoxDrv.kext (Oracle America, Inc., 6.1.14)

Avast High Sierra System Extension Blocked High Sierra 10 13 5

[Not Loaded] VBoxNetAdp.kext (Oracle America, Inc., 6.1.14)

Avast High Sierra System Extension Blocked Chrome


[Not Loaded] VBoxNetFlt.kext (Oracle America, Inc., 6.1.14)

Avast High Sierra System Extension Blocked Download

[Not Loaded] VBoxUSB.kext (Oracle America, Inc., 6.1.14)
The trick of going to the Security System Preference didn't work, since there is no button to trust Oracle. Is there any other way to tell the Mac to load those extensions?

Avast High Sierra System Extension Blocked Mac


Avast High Sierra System Extension Blocked Windows 10

And, since I don't remember having changed anything in my system (apart for the usual cleaning with Cocktail), does this reveal some other type of issue?
Thanx!
Avast High Sierra System Extension Blocked

Avast High Sierra System Extension Blocked Legacy Developer Hp

Paolo