The author mentions this finding was marked as out-of-scope when they reported it to Bitwarden. A couple of categories that are considered out-of-scope are listed, namely: attacks requiring physical access to a user's device, and "other side of airtight hatchway"[0] type issues.
The latter seems reasonable, if the assumption is that the device is fully compromised, and ongoing surreptitious monitoring of user activity by an attacker is occurring.
However, users probably have the reasonable expectation that if their laptop is stolen, their device-local vault data(supposedly encrypted on disk) is not compromised as a result. Bitwarden should either disallow weak pins/pin-access altogether, or they should caveat more clearly the weaknesses of pin-only access to device-local vault data.
The latter seems reasonable, if the assumption is that the device is fully compromised, and ongoing surreptitious monitoring of user activity by an attacker is occurring.
However, users probably have the reasonable expectation that if their laptop is stolen, their device-local vault data(supposedly encrypted on disk) is not compromised as a result. Bitwarden should either disallow weak pins/pin-access altogether, or they should caveat more clearly the weaknesses of pin-only access to device-local vault data.
[0]: https://devblogs.microsoft.com/oldnewthing/20060508-22/?p=31...