Some of my previous rants mention a web application that I wrote for my then-employer. As it is still in use and I have the whole code, too, I figured to check on security a little with a friend. It's all fine, except for one page, were I was sloppy and didn't escape strings, thus allowing for SQL injection.
This is however only possible if already logged in, which has shown to be secure (and the tool is for employees only).
Nobody is ever going to find out, as the only one who knew what injection even is was me. I left 2 years ago.