Confluence Shows Unreadable CAPTCHA
Platform Notice: Data Center Only - This article only applies to Atlassian products on the Data Center platform.
Note that this KB was created for the Data Center version of the product. Data Center KBs for non-Data-Center-specific features may also work for Server versions of the product, however they have not been tested. Support for Server* products ended on February 15th 2024. If you are running a Server product, you can visit the Atlassian Server end of support announcement to review your migration options.
*Except Fisheye and Crucible
Symptoms
Users get a completely unreadable CAPTCHA, for instance when they failed to login to Confluence. Here is an example screenshot:
Cause
Unsupported version of Oracle JDK or a non-standard JDK is used such as OpenJDK.
Resolution
Download the standard and supported Oracle JDK according to supported platforms.
Configure Confluence to use the standard JDK.
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