Over this Labor Day weekend developers at Twitter had to do a bit of additional labor that they should have previously completed - and that's to close a potentially dangerous cross-site scripting (XSS) vulnerability before things slid out of hand.According to the XSSed project, a researcher who goes by the handle "cbr" found and announced an XSS vulnerability on Twitter's site on July 29, 2010. The flaw had gone unfixed ever since.

That is until security researcher Mike Bailey, using the flaw, crafted a proof-of-concept exploit that created a rogue message posting from any account of any logged-in Twitter user who happened to click on a specially crafted button.

Real quickly, an XSS vulnerability is a web application vulnerability that makes it possible to inject client-side scripts into web pages.

In his post, Bailey described these types of XSS flaws as brutally simple to exploit. Just the type of flaw one would expect to be caught in development:

It may surprise some, but I really haven't been big on XSS lately, mostly because it's a problem that hasn't changed for years, and the most basic form of it is still brutally simple to exploit. Not a lot of excitement in it, I guess. But that doesn't mean that it doesn't deserve attention- in fact, that's exactly why it does. So when a new Twitter XSS popped up on my feed reader this morning, I took the 10 minutes it takes to write a proof of concept, and put together an exploit.

Over the summer a number of other XSS flaws have been reported, and fixed, to Twitter, including one on the main Twitter.com and support.twitter.com Web pages.

Now, within about 12 hours of Bailey posting his proof-of-concept, Twitter fixed the flaw. That's not bad time. However, it had been more than four weeks since the flaw was first made public: and that's atrocious for something they obviously could have fixed much, much more quickly.

It's time for Twitter to step up the quality control of its development processes.

Nonetheless, the flaws haven't managed to keep me away. For my security and technology observations throughout the day, you can find me on Twitter.