1986615 - Set network overwrite (devtools) crashing Firefox

Status: RESOLVED FIXED

(DevTools :: Netmonitor, defect, P2)

Description

[Niels]

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:142.0) Gecko/20100101 Firefox/142.0

Steps to reproduce:

I've followed steps as documented under:
https://firefox-source-docs.mozilla.org/devtools-user/network_monitor/network_overrides/index.html

Go to an network call in devtools → Set Network overwrite → Choose to save the file in the downloads directory → reload the page

I am on mac os 15.6.1 MBP M3, but I've seen this behavior as well on windows 10 & 11 devices of colleagues.

Actual results:

After page reload, firefox crashes and needs to be restarted

Expected results:

The page should reload with our specified network call response being replaced with the content in our saved file.

Comment 1

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

The Bugbug bot thinks this bug should belong to the 'Core::Networking' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

Comment 2

[Sunil Mayya]

Hello Niels,
I could not reproduce this issue on my Mac.
We would need some logs to analyze this further.
Could you please share the crash-id for this? You can find this in about:crashes.
Moving this to devtools for further follow-up on this.

Comment 3

[Niels]

Hi Sunil,
Here is the requested information of the submitted crash (re produced today).

crash-id: AF7F9417-93D3-4BF2-B75D-703978C20534

Report contents:
AdapterVendorID: 0x106b
AvailablePhysicalMemory: 76185600
AvailableSwapMemory: 1747779584
BackgroundTaskMode: 0
BuildID: 20250827004350
ContentSandboxCapable: 1
ContentSandboxLevel: 3
CrashTime: 1757317859
DOMFissionEnabled: 1
DOMIPCEnabled: 1
EMCheckCompatibility: true
EventLoopNestingLevel: 1
GpuSandboxLevel: 0
GraphicsNumActiveRenderers: 0
GraphicsNumRenderers: 1
HeadlessMode: 0
InstallTime: 1756886941
LastStartupWasCrash: 0
MacAvailableMemorySysctl: 67
MacMemoryPressure: Normal
MacMemoryPressureCriticalTime: Unset
MacMemoryPressureNormalTime: 1757317729
MacMemoryPressureSysctl: 1
MacMemoryPressureWarningTime: Unset
MozCrashReason: MOZ_RELEASE_ASSERT(!LoadRequireCORSPreflight() || LoadIsCorsPreflightDone()) (CORS preflight must have been finished by the time we call OnStartRequest)
NimbusEnrollments: 1-callout-contextual-chatbot-suggestion-treatment-a-tab-switching-copy-rollout:treatment-a-tab-switching-copy,account-adoption-app-menu-rollout:treatment-a,account-adoption-callout-passwords-global-rollout:treatment-e,address-bar-update-rollout-v1:rollout,ai-chatbot-page-summarization-mvp-treatment-a-callout-badge-rollout:treatment-a-callout-badge,chips-rollout-to-firefox:control,context-id-rotation-every-30-days:control,custom-wallpapers-no-message-rollout-release:control,deprecate-ipaddrany-rollout-for-release:control,desktop-release-rollout-show-relay-to-all-browsers-next-sign-up-modal-cta:next-sign-up-modal-cta,device-migration-accounts-toolbar-icon-rollout:treatment-a,disable-ads-startup-cache:control,disable-enrollment-status-telemetry-for-firefox-desktop-via-nimbustelemetry:control,enable-nimbus-sql-datastore:control,encrypted-client-hello-fallback-mechanism:control,enforce-crlite-results-and-limit-use-of-ocsp-rollout:enforce,fox-doodle-multi-action-cta-2025-rollout:treatment-a,fx-accounts-ping-release-rollout-2:control,login-status-advisory-callout-rollout:treatment-a,long-term-holdback-2025h1-growth-desktop:delivery,mozilla-vpn-in-private-browsing-treatment-d-rollout-en-only:treatment-d,one-click-sponsored-settings:control,pdf-annotations-highlight-treatment-b-rollout:treatment-b,report-this-ad:control,smart-tab-groups-rollout-beta:smart-tab-groups,spoc-positions-and-placements-rollout:control,storage-access-heuristic-restriction-rollout:treatment-branch,unified-api-for-spocs-and-top-sites-controlled-rollout-for-release-133:control,unified-search-button-callout-rollout-v1:control,visual-card-updates:updated
Notes: FP(D10-L1000-W0000000-T01) WR? WR+ GL Context? GL Context+
ProductID: {ec8030f7-c20a-464f-9b0e-13a3a9e97384}
ProductName: Firefox
PurgeablePhysicalMemory: 1560510464
RDDProcessStatus: Running
ReleaseChannel: release
SafeMode: 0
SecondsSinceLastCrash: 430856
StartupCacheValid: 1
StartupCrash: 0
StartupTime: 1757317729
SubmittedFrom: Client
TelemetryEnvironment: {"build":{"applicationId":"{ec8030f7-c20a-464f-9b0e-13a3a9e97384}","applicationName":"Firefox","architecture":"aarch64","buildId":"20250827004350","version":"142.0.1","vendor":"Mozilla","displayVersion":"142.0.1","platformVersion":"142.0.1","xpcomAbi":"aarch64-gcc3","updaterAvailable":true},"partner":{"distributionId":null,"distributionVersion":null,"partnerId":null,"distributor":null,"distributorChannel":null,"partnerNames":[]},"system":{"memoryMB":36864,"virtualMaxMB":null,"cpu":{"count":14,"cores":14,"pcount":10,"mcount":0,"ecount":4,"vendor":"","name":"Apple M3 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Throttleable: 1
TotalPhysicalMemory: 38654705664
URL: https://www.google.com/?zx=1757317770536&no_sw_cr=1
UptimeTS: 132.25
UtilityProcessStatus: Running
Vendor: Mozilla
Version: 142.0.1
useragent_locale: en-US
This report also contains technical information about the state of the application when it crashed.

Comment 4

[Niels]

Seems it changed after submitting it?
bp-4c907ef0-790b-4a12-8789-5e2760250908
https://crash-stats.mozilla.org/report/index/4c907ef0-790b-4a12-8789-5e2760250908

Comment 5

[Julian Descottes [:jdescottes]]

I think you are hitting the same issue as Bug 1940738. Basically you are overriding a request which requires a CORS preflight, which will not be received at the appropriate time.

Comment 6

[Niels]

So this means the feature is currently broken (or half working with simple requests only).
As a user I'd still would not expect this to crash the browser, and instead work even if its not a simple request.
Akin to how it works on other browsers (chromium for example).

Is there anything planned to inform the user about these dependencies when trying to use this feature?

Comment 7

[Julian Descottes [:jdescottes]]

(In reply to Niels from comment #6)

So this means the feature is currently broken (or half working with simple requests only).
As a user I'd still would not expect this to crash the browser, and instead work even if its not a simple request.
Akin to how it works on other browsers (chromium for example).

Is there anything planned to inform the user about these dependencies when trying to use this feature?

This is an annoying bug yes, the plan is to fix it.

Comment 8

[Julian Descottes [:jdescottes]]

Attachment: Bug 1986615 - Flag CORS preflight as done from HttpChannel.setResponseOverride

Comment 9

[Julian Descottes [:jdescottes]]

Attachment: Bug 1986615 - [devtools] Update network override test to check CORS preflight scenario

Comment 10

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/780d59378d93
https://hg.mozilla.org/integration/autoland/rev/1744580a69b9
Flag CORS preflight as done from HttpChannel.setResponseOverride r=necko-reviewers,valentin
https://github.com/mozilla-firefox/firefox/commit/9dac9f63e6f7
https://hg.mozilla.org/integration/autoland/rev/046a1f7e0c23
[devtools] Update network override test to check CORS preflight scenario r=devtools-reviewers,bomsy

Comment 11

[Norisz Fay [:noriszfay]]

https://hg.mozilla.org/mozilla-central/rev/1744580a69b9
https://hg.mozilla.org/mozilla-central/rev/046a1f7e0c23

Comment 12

[Julian Descottes [:jdescottes]]

Attachment: Bug 1986615 - Flag CORS preflight as done from HttpChannel.setResponseOverride

Original Revision: https://phabricator.services.mozilla.com/D264973

Comment 13

[Phabricator Automation]

firefox-beta Uplift Approval Request

• User impact if declined: Avoids a potential crash while using a DevTools feature.
• Code covered by automated testing: yes
• Fix verified in Nightly: yes
• Needs manual QE test: no
• Steps to reproduce for manual QE testing: N/A
• Risk associated with taking this patch: low
• Explanation of risk level: The updated code is only triggered by DevTools network override feature and should not impact regular users.
• String changes made/needed: N/A
• Is Android affected?: no

Comment 14

[Julian Descottes [:jdescottes]]

Attachment: Bug 1986615 - [devtools] Update network override test to check CORS preflight scenario

Original Revision: https://phabricator.services.mozilla.com/D264974

Comment 15

[Pulsebot]

https://github.com/mozilla-firefox/firefox/commit/db7b8b2aa708
https://hg.mozilla.org/releases/mozilla-beta/rev/9d8115b4ca46
https://github.com/mozilla-firefox/firefox/commit/eff82fc56aa0
https://hg.mozilla.org/releases/mozilla-beta/rev/eebfcc927c7d