Adobe Photoshop CS4 Update is an official safety update for the famous design program by Adobe. If you use this version, it is highly recommended that you apply it to your installation.
Adobe Photoshop CS4 Update solves various vulnerability problems that are present in the current Photoshop CS4 version and in its previous update. This vulnerability allowed the execution of certain types of malicious files that could cause losing control of the system.
Additionally, the Adobe Photoshop CS4 Update solves certain stability problems with the brush, styles and gradient tools. If you use them often, you will be able to work better from now on.