SmartScreen Application Reputation, with Pictures

Last Update: Sept 3, 2025 I’ve previously explained how Chromium-based browsers assign a “danger level” based on the type of the file, as determined from its extension. Depending on the Danger Level, the browser may warn the user before a file download begins in order to confirm that the user really wanted a potentially-dangerous file.Continue reading “SmartScreen Application Reputation, with Pictures”

Browser SSO / Automatic Signin

Last Update: 8 March 2024 Over the years, I’ve written a bunch about authentication in browsers, and today I aim to shed some light on another authentication feature that is not super-well understood: Browser SSO. Recently, a user expressed surprise that after using the browser’s “Clear browsing data” option to delete everything, when they revisitedContinue reading “Browser SSO / Automatic Signin”

How do Random Credentials Mysteriously Appear?

One commonly-reported issue to browsers’ security teams sounds like: “Some random person’s passwords started appearing in my browser password manager?!? This must be a security bug of some sort!” This issue has been reported dozens of times, and it’s a reflection of a perhaps-surprising behavior of browser login and sync. So, what’s happening? Background EvenContinue reading “How do Random Credentials Mysteriously Appear?”

Improving Native Message Host Reliability on Windows

Last Update: Nov 28, 2023 Update: This change was checked into Chromium 113 before being backed out. The plan is to eventually turn it on-by-default, so extension authors really should read this post and update their extensions if needed. The feature was relanded inside Chrome Canary version 115.0.5789.0. It’s off-by-default, behind a flag on theContinue reading “Improving Native Message Host Reliability on Windows”

Q: “Remember this Device, Doesn’t?!?”

Q: Many websites offer a checkbox to “Remember this device” or “Remember me” but it often doesn’t seem to work. For example, this option on AT&T’s website shown when prompting for a 2FA code: …doesn’t seem to work. What’s up with that? A: Unfortunately, there’s no easy answer here. There is no browser standard forContinue reading “Q: “Remember this Device, Doesn’t?!?””