1805967 - Freeze `rv:` segment in the User Agent string to `rv:109.0` to avoid erroneous IE11 detection

Status: RESOLVED FIXED

(Web Compatibility :: Interventions, defect, P1)

Description

[Dennis Schubert [:denschub]]

As per this investigation, it looks like there is a server-side UA sniffing issue on bestbuy.com - which can be worked around by capping the version number to 109. So let's prepare to do that, as we can always back that intervention out if our outreach succeeds.

Note that this might also be relevant on bestbuy.ca and potentially other ccTLDs.

Comment 1

[Chris Peterson [:cpeterson]]

I can reproduce this bug with Firefox versions 110-119 on Windows. Versions >= 120 work fine.

Comment 2

[Outvi V]

With a Firefox 110 on Linux I cannot reproduce the Bestbuy problem, but I came across one on another website: https://www.bilibili.com/read/cv14753471

Let me pick the piece of code at the head of this page that causes the chaos:

0 < navigator.userAgent.indexOf('rv:11')

I guess it's trying to detect IE 11 since IE 11 user agent also contains the string "rv:11":

Mozilla/5.0 (Windows NT 6.3; Trident/7.0; rv:11.0) like Gecko

Comment 3

[Kelsey Gilbert [:jgilbert]]

Here's another one on cvs.com: https://webcompat.com/issues/115559

Comment 4

[Kelsey Gilbert [:jgilbert]]

[Tracking Requested - why for this release]:

I believe that this set of issues should be at least an S2 for the Firefox product, and should block Release.
These issues with these mainstream websites will definitely push users away from Firefox.

Comment 5

[Kelsey Gilbert [:jgilbert]]

Affected:

navigator.userAgent
"Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:110.0) Gecko/20100101 Firefox/110.0"

Unaffected:

navigator.userAgent
'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/110.0.0.0 Safari/537.36'

Comment 6

[Pascal Chevrel:pascalc (PTO until April 26)]

https://github.com/webcompat/web-bugs/issues/115403 this is a major site in France, affected by the same issue. I suspect this is the tip of the iceberg.

Comment 7

[BugBot [:suhaib / :marco/ :calixte]]

The bug is marked as blocking firefox110 (nightly). However, the bug still isn't assigned.

:denschub, could you please find an assignee for this tracked bug? If you disagree with the tracking decision, please talk with the release managers.

For more information, please visit auto_nag documentation.

Comment 8

[:Gijs (he/him)]

Attachment: Bug 1805967 - cap rv: bits in User Agent string to 109 because some sites detect IE11 based on rv:11*, r?#necko-reviewers

Comment 9

[Dennis Schubert [:denschub]]

I have tested the known breakage on webcompat.com, as well as bilibili.com, and can confirm that with Gijs' patch, I no longer get blocked. I cannot test leboncoin.fr as they're locking my VPN and my home's static IP out because apparently I'm a robot - but from the testing that Raul did in the report, I'm confident that this fixes the issue as well.

Gijs, I noticed that the current version says rv:110.0 with a minor-version, but your patch only shows rv:109, without minor version. Would it be possible to have it say rv:109.0 instead? I didn't notice any breakage because of that difference, but let's stay on the safe side.

Comment 10

[Dennis Schubert [:denschub]]

Adjusting the bug title to reflect what we're currently planning to do.

Comment 11

[:Gijs (he/him)]

(In reply to Dennis Schubert [:denschub] from comment #9)

Gijs, I noticed that the current version says rv:110.0 with a minor-version, but your patch only shows rv:109, without minor version. Would it be possible to have it say rv:109.0 instead? I didn't notice any breakage because of that difference, but let's stay on the safe side.

Ugh, yes, good catch, I should have done that to begin with. Updated the patch. New trypush.

Comment 12

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/c7d69ab92660
cap rv: bits in User Agent string to 109 because some sites detect IE11 based on rv:11*, r=necko-reviewers,kershaw

Comment 13

[:Gijs (he/him)]

Attachment: Bug 1805967 - keep android the same because the issue doesn't occur there and its tests are unhappy

Comment 14

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/a186000b3a89
keep android the same because the issue doesn't occur there and its tests are unhappy. CLOSED TREE

Comment 15

[Raul Bucata]

(In reply to Dennis Schubert [:denschub] from comment #9)

I have tested the known breakage on webcompat.com, as well as bilibili.com, and can confirm that with Gijs' patch, I no longer get blocked. I cannot test leboncoin.fr as they're locking my VPN and my home's static IP out because apparently I'm a robot - but from the testing that Raul did in the report, I'm confident that this fixes the issue as well.

Gijs, I noticed that the current version says rv:110.0 with a minor-version, but your patch only shows rv:109, without minor version. Would it be possible to have it say rv:109.0 instead? I didn't notice any breakage because of that difference, but let's stay on the safe side.

I can confirm the fix for leboncoin.fr, on both mobile and desktop.

Comment 16

[Pascal Chevrel:pascalc (PTO until April 26)]

(In reply to Raul Bucata from comment #15)

(In reply to Dennis Schubert [:denschub] from comment #9)

I have tested the known breakage on webcompat.com, as well as bilibili.com, and can confirm that with Gijs' patch, I no longer get blocked. I cannot test leboncoin.fr as they're locking my VPN and my home's static IP out because apparently I'm a robot - but from the testing that Raul did in the report, I'm confident that this fixes the issue as well.

Gijs, I noticed that the current version says rv:110.0 with a minor-version, but your patch only shows rv:109, without minor version. Would it be possible to have it say rv:109.0 instead? I didn't notice any breakage because of that difference, but let's stay on the safe side.

I can confirm the fix for leboncoin.fr, on both mobile and desktop.

leboncoin.fr actually fixed their UA sniffing probably because multiple nightly users alerted them on Twitter about it, it works with rv:110 as well.

Comment 17

[Cristian Tuns]

https://hg.mozilla.org/mozilla-central/rev/c7d69ab92660
https://hg.mozilla.org/mozilla-central/rev/a186000b3a89