Livin’ on the Edge: Dude Where’s My Fix?!? (Redux)

In my last post, I showed you how to use OmahaProxy’s Find Releases tool to discover which versions of Chrome contain a given bugfix.

I noted that if you’re using Microsoft’s new Chromium-based Edge, you can look at the edge://version page or this extension to see the upstream Chrome version upon which Edge is based:

Oct 2022 Update: Unfortunately, the edge://version page approach no longer works. The browser has started sanitizing the User-Agent string to zero out all of the sub-build number information in the User-Agent string, such that Edge will now claim e.g. Chrome/106.0.0.0. I’ve filed a bug on the Edge team asking them to add a new field to the edge://version page. The extension works properly:

Until today, I never realized that this version number can be off-by-one. I noticed this discrepancy after complaints about a nasty bug in Edge that caused a bunch of webpage renderers to crash. The fix, we learned from OmahaProxy, landed in version Chrome Canary 78.0.3872.0.

When Edge next updated, I was alarmed to see that the crash was still present, but the user-agent header contains Chrome/78.0.3872.0, the version that’s supposed to have the fix.

What’s going on?

Chromium’s src/chrome/VERSION file gets updated shortly after the prior Chrome Canary ships, as you can see in this timeline:

1. At 03:13 on Aug 1, /src/chrome/VERSION was updated to 3872.
2. Around 04:00 on Aug 1, Edge’s code pump ingested all of the commits from upstream Chromium into our internal integration branch, preparing for our 78.0.242 Canary build.
3. At 11:20 on Aug 1, the fix for the crash landed.
4. At 23:16 on Aug 1, the last commit from Chromium Master that went into Chrome Canary 78.0.3872 landed.
   Within a few hours, the Canary branch was declared an Official release.
5. At 03:13 on Aug 2, /src/chrome/VERSION was updated to 3873.

Because Edge’s code pump pulled between when the version number was bumped to 3872 [1] and when the crasher’s fix landed [3], Edge ended up with a build that has the 3872 version number, but without the fix that went into Chrome Canary 78.0.3872.

So, for the moment at least, the safe way to be sure that a given Edge build has a given Chromium fix is to ensure that the Chrome token in the user-agent string is later than the Chrome Canary build number in which the patch first shipped.

-Eric