Over the last 25 years Unicode has succeeded. It hasn't displaced all other character encodings, but it's clearly on its way there. It's supported widely enough that it's a compatible choice, new projects use it, and it's becoming the default for more and more systems. Because it can encode nearly every writing system ever used, however, it is extremely complex. This complexity means that most people who interact with it, programmers and otherwise, aren't aware of all it's strange twists. What security issues have come up over the last decade of increasingly widespread use, and do we expect more in the future?