Gallery 3.0.5 is now available for download. It contains several security fixes as well as a handful of new features. The only major security issue involves someone malicious accessing a copy of Gallery 3 that is not yet installed, so if you already have Gallery 3.0.4 installed and configured there are no known major issues. However, as always we strongly recommend that you upgrade to the latest code. Go on, do it. It's fast and painless.
We'd like to thank the following individuals for responsibly reporting these security issues: Michael T. Boos, AMol NAik, Johannes Dahse, Sergey Markov, James 'albino' Kettle, and Johannes Dahse. For their efforts, they will each be receiving bounties of between $100 and $1000 for their help in making Gallery more secure. Read our Bounties page for details and how to submit any security issues you find.