Some ago, I filed #978 to help with the backlog of security bugs with unlanded tests by reminding people to land their tests. The full explanation can be seen in that issue and I recommend skimming it once more.
It looks like this was closed in a forward-looking way that people can use reminders in the future, which is nice.
However, this does not deal with the pre-existing bugs that have no reminder and a reviewed patch attached which has never been landed. It would be nice if we could also solve that.