I’m running Avast v9.0 (41877) on Mac OS X 10.9.4.
In Safari (7.0.5), with the Avast Safari extension installed, the “https” button with the lock icon (that appears to the left of the URL) only shows for a fraction of a second when visiting a secure site, then it disappears. There’s then no way in Safari to confirm that the page is secured, or to view the site’s certificate.
Turn the Avast Safari extension off or removing it allows the “https” button to appear as it should.
Seems like a bug…
On the same topic…I had Avast Web Shields turned off, yet this Safari Extension remained installed and active. I’m a technical person so I figured it out, but that shouldn’t be the case. If the user unchecks “Web Shield” in the Avast prefs, it should remove any web-browser extensions like that, and replace them if the user turns it back on.