wired[.]com/story/amd-chip-sinkclose-flaw/?s=31
tomshardware[.]com/pc-components/cpus/sinclose-vulnerability-affects-hundreds-of-millions-of-amd-processors-enables-data-theft-amd-begins-patching-issue-in-critical-chip-lines-more-to-follow
bleepingcomputer[.]com/news/security/new-amd-sinkclose-flaw-helps-install-nearly-undetectable-malware/
amd[.]com/en/resources/product-security/bulletin/amd-sb-7014.html
Malware is designed to escape detection and stick around -- its masters want the infection to last forever so they can continue to use the device they've taken over. Antivirus software OTOH wants to detect malware and remove it. The only way for malware to completely evade AV software is to infect the PC outside of Windows, because that's where AV software lives. When you turn on a PC the BIOS is the 1st thing that starts, and its mini OS starts the boot loader that Windows devices store on the EFI partition. Both are ideal targets for malware, and fortunately, both are hard to infect.
The newly discovered vulnerability, called Sinkclose by the researchers that discovered it, and SMI Lock Bypass by AMD, allows cyber-criminals that have already infected a PC to further infect the BIOS. It's not an easy attack, & at least at first, home users are less likely to see it -- eventually less advanced &/or skilled criminals may get access to a tool developed by state sponsored cyber-criminals for example, which has happened in the past. The pair of security researchers have not released their code [proof of concept] at AMD's request, and AMD has developed a fix that it's making available to manufacturers to incorporate in new BIOS firmware. You do want to watch for and install the new firmware as soon as it's available -- according to the researchers, if your BIOS becomes infected via this attack, the only user accessible cure is replacement, meaning a new device or at least a new motherboard.
The bottom link above leads to AMD's site, where they list the CPUs and the AGESA version containing the fix. That can be important -- the manufacturer of the motherboard in this PC does not give a thorough explanation of what's new in a BIOS firmware update, but they do list the AGESA version.
wikipedia[.]org/wiki/AGESA