Bulletproof TLS Newsletter #70
Chrome developers want to eliminate mixed content
29 Oct 2020
Author: Hanno Böck

This issue was distributed to 55,913 email subscribers.

Bulletproof TLS Newsletter is a free periodic newsletter bringing you commentary and news surrounding SSL/TLS and Internet PKI, designed to keep you informed about the latest developments in this space.

In this issue:

  1. Chrome developers want to eliminate mixed content
  2. Short news

Chrome developers want to eliminate mixed content

The current Chrome version no longer loads mixed content on HTTPS connections. This change was announced by the Chrome security team last year and has now been implemented. Emily Stark from Chrome’s security team explains some of the details on Twitter.

When a web page is loaded via encrypted HTTPS to load subresources like images or videos via unencrypted connections, this is called mixed content. This can be a security risk because attackers can read and modify the unencrypted connections.

Browsers blocked active mixed content, including Javascript and CSS files, for many years. However, having passive content like images or videos as mixed content was still allowed.

Chrome changes this behavior now. If an HTTPS web page tries to load such content via HTTP, it will automatically try to load the content via HTTPS. If that doesn’t work, the loading is blocked. Mozilla plans to adopt this behavior as well, and there is work underway for standardizing it.

There is a special case in which mixed content warnings still appear: forms loaded from HTTPS web pages that have HTTP targets. Changes for this case are planned for version 87, including Chrome showing a warning while a user is typing into such forms and a full page warning before submission.

Short news