In CMS, while in the Shift+Click popup form, clicking a UI action causes the popup to become an empty window and remain open.

In an affected instance:

1. Navigate to Self-Service > Service Catalog.
2. Select any item (for example, Top Requests > Access), and submit a request to generate an RITM.
3. Launch CMS: https://<instance>.service-now.com/ess
4. Click Account Settings, and select Open Orders.
5. Shift+Click on the RITM number to open the popup form:
   
   
   
   
6. Enter text into the Additional Comments field.
7. Click Update.
8. Note that the popup window shows an empty page and remains open.
   
   
   
   
9. Repeat steps in standard UI, and note this issue does not occur and that the popup form closes as expected.
   
   

After step 9, manually click the X to close out the popup. The update is saved as expected.