Acrobat Reader DC versions 2021.005.20054 (and earlier), 2020.004.30005 (and earlier) and 2017.011.30197 (and earlier) are affected by an Improper Neutralization of Special Elements used in an OS Command. An authenticated attacker could leverage this vulnerability to achieve arbitrary code execution on the host machine in the context of the current user. Exploitation of this issue requires user interaction in that a victim must open a malicious file.
https://helpx.adobe.com/security/products/acrobat/apsb21-51.html