Author: Prodego

Description:
A blocked user (or user who otherwise can not create pages) is able to create a page through Special:Book, by using the "Save and share your book" feature. The page that is created does not appear to respect any restrictions on the user, including the block status of the user, if the user has the rights to create pages, and if the page violates the TitleBlacklist. There are possibly other restrictions I can't think of at the moment that could be being ignored.

Version: unspecified
Severity: major