Because it no longer receives security updates, it is highly vulnerable to modern exploits embedded in PDF files.

This refers to the specific update patch within the Acrobat X lifecycle. Core Features and Tools

Released originally in late 2010, the "X" (10) generation of Acrobat introduced significant workflow improvements designed for professional document management. The "v10.0.2" designation refers to an early maintenance update that addressed stability and security patches. ProDesignTools Core Capabilities