It doesn’t affect their newest keys, but you can’t upgrade an older key to fix it:
All YubiKeys running firmware prior to version 5.7—which was released in May and replaces the Infineon cryptolibrary with a custom one—are vulnerable. Updating key firmware on the YubiKey isn’t possible. That leaves all affected YubiKeys permanently vulnerable.
It doesn’t affect their newest keys, but you can’t upgrade an older key to fix it: