CVE-2021-28546
Acrobat Reader DC versions versions 2020.013.20074 (and earlier), 2020.001.30018 (and earlier) and 2017.011.30188 (and earlier) are missing support for an integrity check. An unauthenticated attacker could leverage this vulnerability to modify content in a certified PDF without invalidating the certification. Exploitation of this issue requires user interaction in that a victim must open the tampered file.
Source: CVE-2021-28546