Password managers often go through quite some hassle to keep passwords 'safe' in memory. However, I often do not get the attack model of many of those tools. Tools like keepass e.g. go through quite to register a browser plugin. But then anyone with normal user rights can extract that key from the browser and do everything with it. Also this whole 'trust this browser' stuff of web apps seems strange if one e.g. can read the cookie store easily...