A password manager injects credentials into a web browser request. A user can browse to a form provided by a server that includes a password field. A plug-in requests a password for the field from a password manager. The actual password is not provided to the plug-in or the browser. The password manager provides a proxy password that is not the actual password for the field. A request interceptor in a separate process from the browser intercepts the completed request as it is sent to the server and replaces the proxy password with the actual password.