This article was created in response to a support issue logged with K2. The content may include typographical errors and may be revised at any time without notice. This article is not considered official documentation for K2 software and is provided "as is" with no warranties.
All K2 sites are unavailable, when you try to access them you see mostly an empty white page with the following text in top right corner of the page:
[Empty Data Label]
Developed by K2 blackpearl
In your Internet browser console it is possible to see numerous errors similar to this one:
Failed to load resource: the DT.SourceCode.Forms...olPack.KendoUI.js:1 server responded with a status of 500 (Internal Server Error)
This issue can be caused by changes made in the web.config (C:\inetpub\K2 blackpearl), more specifically, it can happen when the following lines are added:
<add name="X-UA-Compatible" value="IE=EmulateIE7" />
<add name="Access-Control-Allow-Origin" value="*" />
<add name="Access-Control-Allow-Headers" value="Content-Type" />
<add name="Access-Control-Allow-Methods" value="GET,POST,PUT,DELETE,OPTIONS" />
<add name="Access-Control-Allow-Credentials" value="true" />
In this case, removing these lines or at least removing <add name="Access-Control-Allow-Origin" value="*" /> resolves the issue experienced within the K2 sites.