Measuring Progress

In the reasonably short time that I've been involved with Mozilla, we've made amazing changes to the web and our Firefox browser. We've seen the adoption of HTML5, open video, and a slew of other features. This means the web is yet even more complex and by extension, so is Firefox.

Sometimes Firefox doesn't perform as well as it should, and it's hard for us to understand why.

Enter the Telemetry project. Our performance team, led by Taras Glek, developed a feature that lets us measure performance-related stuff as you use Firefox. Starting with the version of Firefox released today, you have the opportunity to opt-in to send us some of these statistics. They're not tied to you, and we will take a look at the data in aggregate to see if there are widespread problems in the various bits of Firefox's plumbing.

I posted a note about this over on The Mozilla Privacy Blog. As we deployed this feature, we worked hard to make sure that our users will have choice and control of the data they send us. This involves a few bits of critical thinking: first, we have to make sure you're not surprised about this.  Second, we make sure that we're only collecting what we need to make Firefox better. Third, our practices must be transparent (and not just open source, like we try to be clear about what we collect).  Fourth, we make sure that you know you're sending us this data and can make it stop if you want.

We wrote down how telemetry works for you to read (if you want) and how the feature lines up with our promises put forth in the Privacy Operating Principles that we've been working with for a while now. As we add new probes to telemetry to see where to improve Firefox, we'll be cataloging those as well, including risk analysis for stuff that's remotely private.  We'll never collect stuff like your address or credit card numbers through this system (that'd be weird), but we may want to know which of the add-ons you're using that are slowing down Firefox.

This risk analysis and privacy review are the things we plan to do with new Firefox features that involve your data; whether or not we collect anything, it's important that we live up to the operating principles we've put out, and Telemetry is an early example of how we plan to keep you in control.

Careful... pixel-data access is pointy

Robert O'Callahan writes:

Some Web applications require the pixel data of Web pages to be exposed to Web applications [...] There are some pretty big security implications here. The biggest problem is cross-origin information leakage.

He's right on. This has a bunch of subtle risks to haphazardly implementing pixel-data access. The one near and dear to my heart is the risk of defeating what we shipped a while back to stop the CSS- and JavaScript-based history sniffing. Draw links, read colors, defeat fix. Not good. We can't just lie to the content script attempting to access the rendered data -- once it's drawn, it's really hard to figure out what's a link and what isn't. So what do we do? Take a look at this and the other issues with implementing pixel-data access over on his blog. If you've got ideas, we're all ears.

mozilla privacy blog

Hey, good news! Mozilla has a privacy blog where we will be blogging about all sorts of privacy stuff.

I'll continue to write about it here, but check it out for more reading. The latest post by Alex Fowler announces a field guide to DNT that discusses what to do when you receive the header, and what some other sites are already doing. He also talks about how many people have turned on DNT.

Check it out: Mozilla Privacy Blog