Critical vulnerabilities have been identified in Adobe Photoshop CS4 and earlier versions.
Critical is Adobe's highest vulnerability rating and could when exploited allow malicious native-code to execute, potentially without a user being aware.
More information is available in Adobe's security bulletin 10-13. Download link to upgrade current installation to the version CS4 11.0.2 is also available from this security bulletin. Alternatively, use Photoshop's built-in functionality to check for updates.
Note that Photoshop CS5 is not affected by this vulnerability.
Norman recommends that users update their Adobe Photoshop installation as soon as possible.