Mambo 4.5.3 to 4.5.3h Patch Installation Instructions:

Below you will find the steps to bring a Mambo 4.5.3 system up to the 4.5.3h version.  This will NOT bring prior versions up to date.  You should first try to bring prior versions up to the 4.5.3 patch level before applying the 4.5.3h patch.  There is another patch you can use to bring you from a 4.5.2.3 to 4.5.3h if you are running that version.

Step 1: Backup your site (both database & site files).

Step 2: Take your site offline:  Site->Global Configuration->Site Offline (YES).

Step 3: Extract all files inside the patch into your Mambo installation. The files are organized in a hierarchy identical to your 4.5.3 install. Let them overwrite the existing files.

Step 4: Bring your site back online:  Site->Global Configuration->Site Offline (NO).

That's it.  Patch complete.