Wiki does not respect repository r/w permissions (BB-11343)

From our customer's issue report:

We have an 25 users account on Bitbucket: "[redacted]". A set of users has only read access to one repository "repo [redacted]", and no other rights to any other repo from our team. The read access works fine for the source code, they cannot commit. But on the private wiki they seem to have write possibilities, in contrast to the statement: "For a private wiki, a user's access to the code repository also applies to the wiki.".
To reproduce, login through portal with read only account on repo, goto repo, wiki, and select edit. Then change and save.