CVE-2026-41571: Note Mark: OIDC-registered users authenticated by submitting password "null"

Note Mark is an open-source note-taking application. In version 0.19.2, IsPasswordMatch in backend/db/models.go falls back to a hard-coded bcrypt("null") placeholder whenever a user has no stored password. OIDC-registered users are created with an empty password, so anyone who submits password: "null" to the internal login endpoint receives a valid session for that user. The bypass is unauthenticated and requires no user interaction. This issue has been patched in version 0.19.3.