Mozilla launched Firefox 87.0 this morning, the latest version of the open source browser. Followed by the heels of December Firefox 85 and February Firefox 86, the new features of the new version ̵
Firefox has been blocking third-party tracking scripts by default for quite some time now. For the most part, this works quite seamlessly – but in some cases, missing tracking scripts can interfere with the rendering of a page, either delaying it (as shown in the animated image on the left) or destroying it permanently.
Smart Block takes an extra step to improve rendering on pages that build in third-party trackers – instead of just pulling the script and leaving a “hole” where it used to be, Smart Block replaces it with what Mozilla describes as “stand-alone” These stand-in scripts work just like the original trackers to recover the intended page playback sequence and results without actually leaking data to third parties.
Mozilla sources much of its data on what is – or is not – a “regular tracking script” that needs a Smart Block engagement from the Disconnect Tracking list.
Improved reference trimming
When you post an image from another site on your own site, information about the site’s viewers leaks to the operators on the other site. To illustrate this, let’s imagine that the operators of
greatsearch.tld, a fictional search engine, includes an image of a sheep from
sheep-pictures.tld on each results page.
The HTML code for the embedded image is simple:
When users of
greatsearch.tld uses the site, their browsers see that code and download automatically
https://sheep-pictures.tld/sheep1.jpg while rendering the page.
Traditionally, the entire URL of the referring page is included in that web request … which means information leakage to the operators of
sheep-pictures.tld, who wanted to see something like this in their logs:
240.163.255.110 - - [15/Mar/2021:10:28:57 -0400] "GET /sheep1.jpg HTTP/1.1" 200 11676 "http://greatsearch.tld/res ults?really-embarrassing-medical-condition"
Now that we understand the reference field itself, it’s pretty clear what “reference trimming” means – and why Mozilla is becoming more aggressive with it. If the user above used Firefox 87 when doing the same search, the operators will off
sheep-pictures.tld will instead see the following log entry:
240.163.255.110 - - [15/Mar/2021:10:28:57 -0400] "GET /sheep1.jpg HTTP/1.1" 200 11676 "http://greatsearch.tld/"
More solutions and features
Firefox 87.0 also offers enhancements to the Highlight All feature in Find in Page, full support for macOS ‘built-in screen reader VoiceOver, and several minor UI enhancements, security updates, and general customizations. For the full list, go to Mozilla’s own release notes for Firefox 87.0.