Browser integration is a connection between a desktop application and a web browser, commonly implemented through a browser extension and a messaging channel between the extension and the desktop app. For a password manager, this can let the browser request matching credentials or fill login forms without exposing the vault to every webpage.
This connection is a security boundary: weak authentication, unsafe message handling, or overly broad permissions can let malicious software or webpages misuse the bridge. Real attacks may target the extension, the desktop messaging component, or the data exchanged between them. Defenses include restricting which extensions and origins can communicate, validating every request, minimizing permissions, and keeping both the app and extension updated.