In an attempt to improve the security of its users, the Chrome browser will soon start blocking insecure downloads on HTTPS pages, Google announced.
The plan, which the Internet giant laid out this week, is expected to be completed sometime in the fall, when Chrome 86 arrives.
The announcement comes just days after the release of Chrome 80, which by default blocks mixed audio and video resources if they cannot be automatically upgraded to HTTPS. The same will happen with image files in Chrome 81, which is expected to be released to the stable channel in March 2020.
In the long term, Google’s plan is to block all insecure subresources on secure pages, as they represent a risk for users. Files that are downloaded insecurely could be replaced by attackers with malware, or exposed to eavesdroppers.
“To address these risks, we plan to eventually remove support for insecure downloads in Chrome,” the Internet giant says.
In the initial phase, the focus is on insecure downloads started on secure pages, and the first step is to display warnings. The restrictions for mixed content downloads, Google says, will be pushed to all desktop platforms first.
Executable files will be impacted first, with Chrome 82 displaying a warning on them and Chrome 83 blocking them.
Next in line will be archives and disk image files (a warning in Chrome 83 and blocked starting with Chrome 84), followed by other non-safe file types such as PDF and Word documents (a warning in Chrome 84 and blocking in Chrome 85).
Chrome 85 will warn of mixed content downloads of images, audio, video, and text, and will block all other mixed content downloads, while Chrome 86, which is expected to arrive in the stable channel in October 2020, will completely block all mixed content downloads.
“Chrome will delay the rollout for Android and iOS users by one release, starting warnings in Chrome 83. Mobile platforms have better native protection against malicious files, and this delay will give developers a head-start towards updating their sites before impacting mobile users,” Google says.
To ensure their users never see a download warning, developers should ensure that all files are served over HTTPS only.
For testing purposes, developers can already activate a warning on all mixed content downloads in the current version of Chrome Canary, or in Chrome 81 once released. For that, they need to enable the “Treat risky downloads over insecure connections as active mixed content” flag at chrome://flags/#treat-unsafe-downloads-as-active-content.
For enterprises and educational institutions, Google provides an option to disable blocking on a per-site basis via the InsecureContentAllowedForUrls policy, by adding a pattern that matches the page that requests the insecure download.
“In the future, we expect to further restrict insecure downloads in Chrome. We encourage developers to fully migrate to HTTPS to avoid future restrictions and fully protect their users,” Google concludes.