Microsoft Dynamics. I do not have any details, but somewhere in an "information text" input field, there was
a space to much.
Took down the entire financial system for a big car retailer in Sweden for several days. They were examining servers, running processes, patches... I do not know how they found it, but considering what it turned out to be, it was extremely frustrating.
Our Navision is of course customized to a degree, but I have no details about that either.
Take heed, filter input. Everywhere.