A patch level release contains fixes for only the most critical issues in the previous release. In most cases, these are released to address a security issue. However they can be released for data integrity issues as well.
A patch level is designed to be installed directly over top of your existing installation, with no other action. You do not need to run any upgrade scripts.
How to Upgrade
This is not a full upgrade. You do not need to run any upgrade scripts to complete the upgrade.
Patch: Download a patch file discussed in this thread and upload them to your web server, overwriting the existing files. All patches are available from the Members' Area patch page.
Patch Packages are cumulative so you only need the latest one available for your version. You cannot use a Patch to upgrade your site.
Full Package: Alternatively you can download the full package in the vBulletin Members Area and again upload the affected files mentioned in the release thread.
Patch Level Releases are only supported for their targeted version. If you are using a previous version, you will need to perform a complete upgrade for full functionality and support. Patch Levels will only be released for the latest version in an active vBulletin series.