ImageMagick is a common graphic library in Linux to manipulate images (e.g. resize, crop, etc). It appears in most gallery functionality.
Recently, ImageMagick contains remote arbitrary code execution vulnerability.
If your WordPress plugins use ImageMagick, recommended to disable the plugins temporarily (or set the plugin to use PHP GD library instead), until the upstream release the update, and your web host updated ImageMagick library.
An update has been released by Redhat Enterprise Linux (and CentOS).
If you are using RHEL 6 or 7 (or CentOS 6 or 7), you may yum to update.