Author Topic: Web Shield blocking websites via substituted SSL certificate  (Read 3591 times)

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Offline micoots

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Web Shield blocking websites via substituted SSL certificate
« on: January 30, 2019, 11:08:20 PM »
Hi. Over the past few days the Web Shield component of Avast free (windows 10) has been blocking access to websites. I use Firefox primarily but it blocks on Chrome and others too.

Avast seems to be substituting it's own SSL certificate, which the Web browser sees and doesn't confirm with the remote website. So SSL cert of Avast doesn't authenticate against www.google.com and others.

This results in every SSL enabled website on the web being inaccessible.

All I can do is turn off the web shield component for the websites to work again. I've been using Avast free on Windows 10 for about a year now.

How can this be fixed? Thanks.

Offline DavidR

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Re: Web Shield blocking websites via substituted SSL certificate
« Reply #1 on: January 31, 2019, 12:44:31 AM »
This has to do with the changes in firefox 65, see this topic, https://forum.avast.com/index.php?topic=224885.0

Towards the end are some suggestions, which could help you resolve it.
WinXP ProSP3/ Core2Duo E8300/ 4GB Ram/ avast! free 18.5.2342/ Firefox ESR, uBlock Origin, uMatrix/ MailWasher Pro7.11.0/ DropMyRights/ WinPatrol+/ Drive Image 7.1/ SnagIt 10.0/ avast! mobile security
Windows 10 Home 64bit/ Acer Aspire F15/ Intel Core i5 7200U 2.5GHz, 8GB DDR4 memory, 256GB SSD, 1TB HDD/ avast! free 19.7.2388 (build: 19.7.4674.494)/ WinPatrol+/ Firefox, uBlock Origin, uMatrix/ MailWasher Pro7.11.0/ WinPatrol+/

Offline freeforever03

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Re: Web Shield blocking websites via substituted SSL certificate
« Reply #2 on: January 31, 2019, 02:06:15 AM »
Hi micoots. I had the same problem. After searching the forums for an answer I found a simple solution that doesn't require you to disable the Web Shield. First open the Avast user interface and select the Menu option. Click on Settings, Protection, and Core Shields. Scroll to the Web Shield and click on it.  Then, uncheck Enable HTTPS Scanning. That did it for me. I hope the Avast team comes up with a better solution soon.

Offline DavidR

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Re: Web Shield blocking websites via substituted SSL certificate
« Reply #3 on: January 31, 2019, 02:26:21 AM »
There is a better solution, I suggest that you read the link that I posted.  Disabling https scanning is almost as bad as completely disabling the Web Shield. 

Nowadays most websites are using https and not bog standard http.
WinXP ProSP3/ Core2Duo E8300/ 4GB Ram/ avast! free 18.5.2342/ Firefox ESR, uBlock Origin, uMatrix/ MailWasher Pro7.11.0/ DropMyRights/ WinPatrol+/ Drive Image 7.1/ SnagIt 10.0/ avast! mobile security
Windows 10 Home 64bit/ Acer Aspire F15/ Intel Core i5 7200U 2.5GHz, 8GB DDR4 memory, 256GB SSD, 1TB HDD/ avast! free 19.7.2388 (build: 19.7.4674.494)/ WinPatrol+/ Firefox, uBlock Origin, uMatrix/ MailWasher Pro7.11.0/ WinPatrol+/

Offline freeforever03

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Re: Web Shield blocking websites via substituted SSL certificate
« Reply #4 on: January 31, 2019, 03:49:41 AM »
I took your (DavidR) suggestion and edited the Firefox config file and reset the Web Shield back to checking HTTPS. That worked perfectly. Thanks for the information.

Offline bobby1981

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Re: Web Shield blocking websites via substituted SSL certificate
« Reply #5 on: January 31, 2019, 02:28:43 PM »
Yes, other people have mentioned success by way of deleting each Firefox profile's certificate file (and letting Firefox recreate it), but that doesn't work for me as a fix and I have to disable Avast's HTTPS Scanning in order to use the browser (even if I downgrade to the previous, working 64).  Hopefully Avast will fix this issue ASAP.

Edit: Re-installing Avast didn't work either.
« Last Edit: January 31, 2019, 02:53:06 PM by bobby1981 »

Offline DavidR

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Re: Web Shield blocking websites via substituted SSL certificate
« Reply #6 on: January 31, 2019, 05:49:07 PM »
I took your (DavidR) suggestion and edited the Firefox config file and reset the Web Shield back to checking HTTPS. That worked perfectly. Thanks for the information.

You're welcome.
WinXP ProSP3/ Core2Duo E8300/ 4GB Ram/ avast! free 18.5.2342/ Firefox ESR, uBlock Origin, uMatrix/ MailWasher Pro7.11.0/ DropMyRights/ WinPatrol+/ Drive Image 7.1/ SnagIt 10.0/ avast! mobile security
Windows 10 Home 64bit/ Acer Aspire F15/ Intel Core i5 7200U 2.5GHz, 8GB DDR4 memory, 256GB SSD, 1TB HDD/ avast! free 19.7.2388 (build: 19.7.4674.494)/ WinPatrol+/ Firefox, uBlock Origin, uMatrix/ MailWasher Pro7.11.0/ WinPatrol+/