https://github.com/slockit/DAO/pull/247/commits/b7038eacdc3b8bb07cfb6cb8bcc98dba9e2c9302
They had 2 Pull Requests that attempted to address issue. Here is other one
https://github.com/slockit/DAO/pull/248
Seems that one was never merged as well.
It's been a known problem publically since June 9th. If I can find the link I'll edit this post.
Additionally (I could be wrong on this) the DAO requires two weeks of voting to correct such flaws.
On another thread they said this was a known issue since 2015. Which means they had months to sort it out and didn't bother. Shoddy, shoddy, shoddy.