Starting from Avast 2015 version, Web Shield component in it started scanning for HTTPS websites for malware, this ‘HTTPS Scanning’ feature is enabled by default and has made connecting to secure sites –we daily visit like Google, Facebook, YouTube, Twitter –more  difficult for Firefox users by showing  the following warnings.

READ: Fix: Firefox crashes due to Avast 2015

Errors triggered by HTTP Scanning feature in Firefox for secure websites

‘This Connection is Untrusted

You have asked Firefox to connect securely to, but we can’t confirm that your connection is secure.’

Normally when you try to connect securely, sites will present trusted identification to prove that you are going to the right place. However, this site’s identity can’t be verified.’

After upgrading to Windows 10, Avast shows this certificate warning in Firefox

‘An error occurred during a connection to Peer’s certificate has an invalid signature. (Error code: sec_error_bad_signature)

The page you are trying to view cannot be shown because the authenticity of the received data could not be verified.
Please contact the website owners to inform them of this problem.’

To avoid these issues, you need to disable HTTP Scanning feature in Avast, here is how you can do that.

1. Open Avast user interface

2. Click on Settings > Active Protection, click ‘Customize’ for ‘Web Protection’

3. Uncheck the ‘Enable HTTPS Scanning’ and click ‘OK’.

 Avast 2015 web shield settings

SEE: Avast Browser Cleanup Auto Deletes Firefox Add-ons

Bonus tip: To confirm Avast web shield is scanning connection to an encrypted page in a browser

In that browser, while you’re on HTTPS enabled page, click on the lock icon in the address bar, you’ll see the connection has been verified by Avast Web/mail shield.

In Firefox browser for, it looks like this

connection to verified by Avast Web or Mail shield

CHECK:November 2014 Update for Windows 8.1 Causes Issues to Avast User PCs