The Google Security Team has announced a timeline for when Chrome will begin blocking mixed content by default in order to ensure that HTTPS browsing is more secure. Mixed content refers to HTTPS pages that load resources, such as images, videos, stylesheets, and scripts, over HTTP.
The gradual rollout will begin with Chrome 79, which is scheduled for release in December 2019. The browser already blocks mixed scripts and iframes, but this release will add a new setting (that can be toggled on or off) for users to unblock it on a per-site basis.
The next phase of the rollout will progress with Chrome 80, due in January 2020, where mixed audio and video resources will get auto-upgraded to HTTPS. If they fail to load over HTTPS, Chrome will automatically block them. Mixed images will still load but Chrome will display a “Not Secure” warning in the omnibox next to the URL.
The last phase of the rollout is planned for February 2020. Along with the release of Chrome 81, mixed content images will bet auto-upgraded to HTTPS and Chrome will block them if they fail to load.
The Google Security Team reports that Chrome users now spend more than 90% of their browsing time on HTTPS on both desktop and mobile. The plan to begin blocking mixed content is targeted at addressing insecure holes in SSL implementations of sites that have already made the switch to HTTPS.
WordPress site owners have plenty of time to ensure all their resources load over HTTPS.