This is the one thing I don't like about Joomla. These blasted updates are being released on a regular basis . That means that if you have Joomla 1.5.11, you are at risk? So they've released 1.5.13, I expect a couple of weeks later and 14 will be released. Are we actually safe if we have a slightly older version?
And the other problem is that I use the SEF patch. Last time I looked a few days ago, they haven't even released one for 1.5.12. so if I upgrade my websites, all my meta information goes down the toilet.