1592780 - Empty alerts when browser.xul.error_pages.enabled=false

Status: RESOLVED FIXED

(Firefox :: Security, defect, P5)

Description

[Peter Oliver]

User Agent: Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:69.0) Gecko/20100101 Firefox/69.0

Steps to reproduce:

1. Went to about:config and set browser.xul.error_pages.enabled to false.
2. Browsed to https://expired.badssl.com/

Actual results:

A window appeared titled "Alert", containing ⚠ and an OK button, but nothing else.

Expected results:

I should have received a message along the lines of "Firefox detected an issue and did not continue to expired.badssl.com. The web site is either misconfigured or your computer clock is set to the wrong time".

It's been a long time since browser.xul.error_pages.enabled=true was made the default. If changing it no-longer works reliably, perhaps it's time for this option to be removed?

Comment 1

[Gingerbread Man]

Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:72.0) Gecko/20100101 Firefox/72.0
20191030050308

gfx.webrender.force-disabled set to true doesn't help, so this isn't bug 1573710.

Comment 2

[Johann Hofmann [:johannh]]

It's been a long time since browser.xul.error_pages.enabled=true was made the default. If changing it no-longer works reliably, perhaps it's time for this option to be removed?

Yeah, I'd say it's to time to say goodbye. Dan, Mike, does one of you have any old time anecdotes on what this is why we might still need it? :)

Comment 3

[Mike Kaply [:mkaply]]

I don't see any reason to keep it. they've been pages for a very long time.

Comment 4

[Daniel Veditz [:dveditz] back January 5, 2026]

WFM, didn't even know we still had this pref.

Comment 5

[Johann Hofmann [:johannh]]

Thanks!

Comment 6

[Jacob Stenson]

Hi there, I would like to work on this. Could you give me some pointers as to what to do to solve it? Thanks
(Requested info from reporter as mentor is away till Dec 3rd)

Comment 7

[Peter Oliver]

(In reply to Jacob Stenson from comment #6)

Hi there, I would like to work on this. Could you give me some pointers as to what to do to solve it? Thanks
(Requested info from reporter as mentor is away till Dec 3rd)

I'm not a Firefox developer, so can only offer very general advice. Start at https://dxr.mozilla.org/mozilla-central/search?q=regexp%3Abrowser.xul.error_pages.enabled&redirect=false. Remove any mention of the setting from the code, and modify anything that tries to use the setting so that it acts as if the setting was set to true. If the tests pass then you probably did it correctly. Good luck!

Comment 8

[Jacob Stenson]

Hi, I am currently working on this bug but running into an issue where when I edit the code in the files found at the link you specified, nothing in the built browser changes. I can even delete entire files and the browser still functions as normal. I understand the reporter of this bug is not a firefox dev so does anyone else have any idea what is going on? Is there something I must do differently to fix this issue compared to other bugs? Thanks

Comment 9

[Mike Kaply [:mkaply]]

Nothing in the built version of Firefox should change. You're removing code that isn't used anymore.

Comment 10

[Jacob Stenson]

I know. I was removing code and testing but nothing was changing. It was as if I had not removed any code at all

Comment 11

[Jacob Stenson]

Am I not also removing the "browser.xul.error_pages.enabled" setting from the about:config page?I have removed all mentions of the code from the files listed in this link: https://dxr.mozilla.org/mozilla-central/search?q=regexp%3Abrowser.xul.error_pages.enabled&redirect=false . but the setting still shows up in about:config and the browser still acts in the same way with regards to the setting being set to true or false.

Comment 12

[Mike Kaply [:mkaply]]

This code is what puts it in about:config

https://searchfox.org/mozilla-central/source/modules/libpref/init/StaticPrefList.yaml#998

Comment 13

[Jacob Stenson]

(In reply to Mike Kaply [:mkaply] from comment #12)

This code is what puts it in about:config

https://searchfox.org/mozilla-central/source/modules/libpref/init/StaticPrefList.yaml#998

I have removed said code and nothing changes in about:config.

Comment 14

[Mike Kaply [:mkaply]]

Is it bold in about:config? That means it was set by you, so it will stick around.

Comment 15

[Jacob Stenson]

(In reply to Mike Kaply [:mkaply] from comment #14)

Is it bold in about:config? That means it was set by you, so it will stick around.

No it isnt bold. Could you try removing the code in StaticPrefList.yaml and see if you run into the same issue?

Comment 16

[Mike Kaply [:mkaply]]

Are you doing an artifact build or a full Firefox build?

Changes to the YAML for preferences requires a full build (since there are cpp/h file changes).

Can you post your patch?

Comment 17

[Jacob Stenson]

Im running "./mach run" in my firefox folder which opens up Nightly, are you saying I have to run "./mach build" to see any changes in about:config? I can post my patch with code I believe will work, although I have not tested it yet.

Comment 18

[Mike Kaply [:mkaply]]

Yes, when you make code changes, you need to do ./mach build to build those changes.

https://developer.mozilla.org/en-US/docs/Mozilla/Developer_guide/Build_Instructions

Comment 19

[Jacob Stenson]

I have not been using ./mach build for previous bugs I have been working on. Is this different due to the fact I am working on cpp/h files? Just to confirm

Comment 20

[Mike Kaply [:mkaply]]

Yes, although I'm surprise you didn't need to build Firefox at all for your other bugs.

Comment 21

[Jacob Stenson]

I built it originally and then started working on bugs, using ./mach run to test the updated code. From now on I'll use ./mach build to test code for this bug!

Comment 22

[Jacob Stenson]

Attachment: Bug 1592780 - Empty alerts when browser.xul.error_pages.enabled=false, r?mkaply

Comment 24

[Johann Hofmann [:johannh]]

It seems like we're blocked on info from Thunderbird devs here and Mike wanted to reach out, has there been any progress?

Comment 25

[Mike Kaply [:mkaply]]

I reached out, but they didn't have an answer (too long ago). I think we should assume they need it and just remove stuff for Firefox only.

Comment 27

[Johann Hofmann [:johannh]]

Anyone we can needinfo on this issue?

Comment 28

[Mike Kaply [:mkaply]]

No, I'll pick up and remove the changes that break thunderbird.

Comment 29

[Tom S. (please needinfo tschuster)]

This person on reddit had this error pages is disabled and it totally broke their browsing experience. We should remove it.

Comment 30

[Mike Kaply [:mkaply]]

Argh. This got reviewed and I didn't get notified. Sorry, I'll get it checked in.

Comment 31

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/3f0183af40d2
Empty alerts when browser.xul.error_pages.enabled=false, r=smaug

Comment 32

[Natalia Csoregi [:nataliaCs]]

https://hg.mozilla.org/mozilla-central/rev/3f0183af40d2