Web Proxy Auto Discovery (WPAD)

Back in the mid-aughts, Adam G., a colleague on the IE team, used the email signature “IE Networking Team – Without us, you’d be browsing your hard drive.” And while I’m sure it was meant to be a bit tongue-in-cheek, it’s really true– without a working network stack, web browsers aren’t nearly as useful. BackgroundContinue reading “Web Proxy Auto Discovery (WPAD)”

Browser Basics: User Gestures

The Web Platform offers a great deal of power, and unfortunately evil websites go to great lengths to abuse it. One of the weakest (but simplest to implement) protections against such abuse is to block actions that were not preceded by a “User Gesture.” Such gestures (sometimes more precisely called User Activations) include a varietyContinue reading “Browser Basics: User Gestures”

Bypassing AppProtocol Prompts

Starting in Microsoft Edge 77 (and Chrome 77), the prompt shown when launching an AppProtocol from the browser was changed to remove the “Always allow” checkbox. That change was made, in large part, because this prompt is the only thing standing between every arbitrary site on the Internet (loaded inside your browser’s sandbox) and aContinue reading “Bypassing AppProtocol Prompts”

Browser Password Managers: Threat Models

All major browsers have a built-in password manager. So we should use them, right? I Do I use my browser’s password manager because it’s convenient: with sync, I get all of my passwords on all of my devices. This convenience means that I can use a different password for every website, improving my security. ThisContinue reading “Browser Password Managers: Threat Models”

Security Zones in Edge

Browsers As Decision Makers As a part of every page load, browsers have to make dozens, hundreds, or even thousands of decisions — should a particular API be available? Should a resource load be permitted? Should script be allowed to run? Should video be allowed to start playing automatically? Should cookies or credentials be sentContinue reading “Security Zones in Edge”

Retiring Internet Explorer

Prelude In late 2004, I was the Program Manager for Microsoft’s clipart website, delivering a million pieces of clipart to Microsoft Office customers every day. It was great fun. But there was a problem– our “Clip of the Day” feature, meant to spotlight a new and topical piece of clipart every day, wasn’t changing asContinue reading “Retiring Internet Explorer”

Disabling TLS/1.0 and TLS/1.1 in the new Edge Browser

UPDATE: Timelines in this post were updated in March 2020, October 2020, April 2021, and October 2021 to reflect the best available information. HTTPS traffic is encrypted and protected from snooping and modification by an underlying protocol called Transport Layer Security (TLS). Disabling outdated versions of the TLS security protocol will help move the webContinue reading “Disabling TLS/1.0 and TLS/1.1 in the new Edge Browser”

Restrictions on File Urls

For security reasons, Microsoft Edge 76+ and Chrome impose a number of restrictions on file:// URLs, including forbidding navigation to file:// URLs from non-file:// URLs. If a browser user clicks on a file:// link on an https-delivered webpage, nothing visibly happens. If you open the Developer Tools console, you’ll see a note: “Not allowed to load local resource:Continue reading “Restrictions on File Urls”

Aw, snap! What if Every Tab Crashes?

For a small number of users of Chromium-based browsers (including Chrome and the new Microsoft Edge) on Windows 10, after updating to 78.0.3875.0, every new tab crashes immediately when the browser starts. Impacted users can open as many new tabs as they like, but each will instantly crash: As of Chrome 81.0.3992, the page will showContinue reading “Aw, snap! What if Every Tab Crashes?”

Web-to-App Communication: App Protocols

Note: This post is part of a series about Web-to-App Communication techniques. Just over eight years ago, I wrote my last blog post about App Protocols, a class of URL schemes that typically1 open another program on your computer instead of returning data to the web browser.  App Protocols2 are both simple and powerful, allowingContinue reading “Web-to-App Communication: App Protocols”