The general rule is that any tricky security code should have as many eyeballs on it as possible, so I'd probably start by seeing if my framework had solid supp

The general rule is that any tricky security code should have as many eyeballs on it as possible, so I'd probably start by seeing if my framework had solid support for this, or failing that, see what popular libraries for my platform exist. In this particular case, the Google Caja project[1] is a good starting place for most HTML/JS/CSS sanitization needs (although the project has a much larger scope than just that); and I think the 'sanitizer' package on npm is a fairly popular wrapper/port of it's basic sanitizing code, and I believe ruby/php/python have their own but I couldn't name them offhand. But it would depend on the exact attack vector you're trying to stop, eg, XSS, remote shell via filename params, etc. If I had to write it myself, I'd probably go for something as braindead as possible; probably a bunch of nested loops backed by some thorough tests. Regexps are great for magic one liners, but magic one liners are antithetical to good security. [1]: https://developers.google.com/caja/ https://developers.google.com/caja/