Outlook blocks opening FQDN and IP address hyperlinks after installing protections for Microsoft Outlook Security Feature Bypass Vulnerability released July 11, 2023
Microsoft released security update KB5002427 for Outlook 2016 on July 11 and security update KB5002432 for Outlook 2013. However, users reported that after installation, the released Microsoft Outlook security feature bypasses the protection of the vulnerability and prevents the opening of FQDN and IP address hyperlinks. Microsoft released the resolution in the latest official log.
Issue
When you click on links in emails in Outlook Desktop where the path is to a fully qualified domain name (FQDN) or IP address you may see the following:
In response to this problem, Microsoft proposed a temporary solution in the recently released official update log. Before proceeding, make sure that the FQDN or IP address added to Trusted Sites is a valid URL path for your company or network. Because this workaround may make the computer or network more vulnerable to attack by malicious users or by malicious software such as viruses.
Resolution
1、Go to Windows Settings and search for and open Internet Options.
2、Click the Security tab, then select Trusted Sites.
3、Add the URL, UNC, FQDN path that you want to allow to “Add this website to the zone“.
For example, add “file://server.usa.corp.com”
Note: If the entry you wish to add does not explicitly start with ‘https:’, you must first uncheck the ‘Require server verification (https) for all sites in this zone’ checkbox before it can be saved.
GPO: User Configuration
Policy: \\Windows Components\Internet Explorer\Internet Control Panel\Security Page\Site to Zone Assignment List
To avoid policy or zone processing failures as a result of incorrect syntax, it is highly advisable to first test the desired policy entry in the Internet Options UI:
The Group Policy zone management interface does not provide input validation of entered values. By leveraging the tip above, administrators can ensure their policy values will be considered valid before deploying them broadly.
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