KB – Possible issue in Desktop Apps after Windows Defender update

Starting around Feb 1st, 2025 many customers with Desktop Apps based deployments may see degradation in startup times on Windows based platforms.  The root of the issue is a recent Windows Defender update and JxBrowser versions < 7.42.0.

Note that BBj 24.22 addresses this issue by updating JxBrowser to 7.42.0.
TeamDev has upgraded the verification mechanism for Chromium binaries to avoid triggering Windows Defender. 

In BBj 24.21 and earlier, the following mitigation steps may be required:

1. Add the directory with Chromium binaries to the whitelist.
2. Rollback the Windows Defender update.

Note:  For details on both of these options, see the What to Do section in the following announcement from TeamDev, the creators of JxBrowser:

What happened

Every time JxBrowser starts, it verifies the integrity of the Chromium binaries. The verification takes 100-200ms on an average machine.

After the Windows Defender update 1.421.1630.0, the verification time increased to several minutes.

What to do

There are two ways to address this situation quickly:

1. Add the directory with Chromium binaries to the whitelist.
2. Rollback the Windows Defender update.

Our recommendation is to add the binaries directory to the whitelist:

1. Locate the Chromium binaries as described here.
2. Go to Start → Settings → Update & Security → Windows Security → Virus & threat protection.
3. Under Virus & threat protection settings, select Manage settings.
4. Under Exclusions, select Add or remove exclusions.
5. Select Add an exclusion, and then select the directory with the Chromium binaries.

What we know

We have noticed that Windows Defender has started paying extra attention to locales/*.pak.info files in the Chromium distribution. When JxBrowser is trying to access each of these files, Windows Defender blocks the Java process for a few seconds.

We have also observed that Microsoft Defender blocks Notepad or Visual Studio Code for a few seconds when attempting to open these files.