Bug in text field causes 403 forbidden after save

When entering a description in the first field below the title, a 403 Forbidden error page appears if you perform the following steps:

Steps to Reproduce:

1. In the description field (below the title), type exactly "Test"! (including the quotes).
2. Press Shift+Enter to move to a new line while staying in the same paragraph.
3. On the next line, type Test.
4. Save.

The following error will show:

Forbidden

You don’t have permission to access this resource.