The server filters out potentially dangerous items in style attributes, but it doesn't filter id or class. They can be used to set style attributes that are otherwise blocked, such as position or creating a lightbox.
Copy-pasting text and formatting from another case can introduce the code used for the buttons on the previous case. This misconfiguration can break the new case page.
For new support cases, the following recommendation can be given to the customers as a workaround for pasting into the editor without introducing additional markup.
- Paste and Match Style on a Mac: Hold down Shift + Option + Command and click V.
- Paste Plain Text in Chrome on Windows: Hold down Shift + Control and click V.