Dear @Nazman1126,
Thank you for this! It seems that the user's router replaces the valid certificate with its own from Cisco Umbrella. Our certificate is issued by Cloudflare and is totally fine, check here - SSL Checker
This might be caused by the use of OpenDNS - https://www.reddit.com/r/techsupport/comments/7qho2u/incorrect_ca_for_ssl_certs/
@Nikita_Kurguzov
Cisco Umbrella is a software we put on all of our computers. My computer has it as well.
Below is a screenshot of the certificate from my computer. It looks just like the certificate from the affected user. Not sure Open DNS is the issue
Dear @Nazman1126,
I'm not sure what exactly is the issue here, but it's clearly caused by the Cisco Umbrella software. Most likely these users have slightly different, more strict security configuration. Your admins need to check and make sure that there is no issue, you can contact Cisco support on this as well.
I am the admin for Cisco Umbrella. All users have the same levels of restrictions.
Dear @Nazman1126,
We still can't help with this. You see what the issue is, and we have no control over third party software. For whatever reason, the certificate issued by the Cisco Umbrella is not trusted on these users' PCs.
I would recommend contacting Cisco support, and just tell them of the issue with the invalid certificate - Cisco Umbrella Global Support
