It's a busy Wednesday in the software mines of Cupertino, as Apple followed up the release of OS X 10.7.4 with a patch to the Safari browser and a tech note detailing how to back out from the password/plain text issue in legacy FileVault accounts and other circumstances.
Safari 5.1.7 patches three Webkit security flaws, but the big change in user-observable behavior is that it will automatically disable any version of Flash Player older than 10.1.102.64. If the plugin is out of date, Safari will gracefully move it aside and offer to download the latest version. Of course, Safari no longer includes the Flash Player plugin by default.
For FileVault or remote home folder users, Apple now recommends upgrading to 10.7.4 followed by a series of steps to change passwords and clear out the log files that may contain the user password in clear text. There are quite a few places where the passwords may have ended up, so be careful to go through all the steps in turn. Apple also provides a set of Terminal commands that will clear the offending logs if needed.