Recently a bug in certain versions of PHP came to the attention of the WordPress developers, this bug could cause a security vulnerability in your any blogs running version 2.0.6 or below blog. It was fairly easy to work around, so they decided to release 2.0.7, just 10 days after the release of 2.0.6, to fix the PHP security problem and the Feedburner issue that was in 2.0.6. It is recommended that everyone running WordPress 2.0.6 or lower upgrade to this new version.
Because this is a much smaller update than previous versions, you do not have to update all of the WordPress files if you’re upgrading from version 2.0.6. Here is the list of files that have changed since 2.0.6:
And just as a reminder, the next major version of WordPress (2.1) is due out by the end of the month, but the 2.0 branch of WordPress will continue to be maintained for several years.