Do you have more than one TB installed, such as a 32-bit version in Program Files (x86) and 64-bit in Program Files? If so, remove everything except 32-bit TB 68.2. No idea what Kaspersky means by 'vulnerable'.

Yes, more than one: 32-bit and 64-bit. The thunderbird.exe 64-bit is v 68.2, and the 32-bit is v 68.1.2. However, the uninstallers for both in Programs and Features shows "(x86 en-US)" in the name. Should I uninstall the 64-bit 68.2 and reinstall from download over the remaining 68.1? Will my emails and address book be preserved?

I just now launched Thunderbird directly from the Programs and Programs(x86) folders, and they are both 32-bit. So I don't have 64-bit, somehow the 32-bit version is in the Programs folder.

Kaspersky probably flags version 68.1.2 because 68.2.0 states in the release notes that there are security fixes against the older release https://www.thunderbird.net/en-US/thunderbird/68.2.0/releasenotes/

Warren said

Yes, more than one: 32-bit and 64-bit. The thunderbird.exe 64-bit is v 68.2, and the 32-bit is v 68.1.2. However, the uninstallers for both in Programs and Features shows "(x86 en-US)" in the name. Should I uninstall the 64-bit 68.2 and reinstall from download over the remaining 68.1? Will my emails and address book be preserved?

Uninstalling any or all versions will not affect your profile folder that has all your mail, address books, settings and other data.