[Bug]: Spoofing user agent is not effective if OS is changed

[stilgarwolf]

Pre-Submission Checklist

• [X] I have checked the existing/closed issues to ensure this issue has not already been reported.
• [X] I am using the latest supported version of the browser.
• [X] I have tried disabling all browser extensions/add-ons to rule out interference from these.
• [X] I have tried clearing the browser cache and cookies.
• [X] I have checked with a new profile and the issue still occurs.
• [X] I have provided detailed step-by-step instructions on how to reproduce the issue.
• [X] I have included relevant screenshots or console outputs.
• [ ] I have checked this problem is not occurring in the latest version of Firefox ESR.
• [ ] This issue is specific to this browser and does not occur in other browsers.

Bug Summary

Spoofing user agent conflicts with script variable window.navigator when the specified operating system is changed.

Same for Browser.

Reproduction Steps

1. For Linux computers
2. Set user agent to "Spoof Chrome on Windows"
3. Check the reported True Operating System Core at https://www.deviceinfo.me

Expected Behavior

True Operating System Core: Windows 10 or 11 version 10.0 (64-bit), or Windows Server 2016 or 2019 or 2022 version 10.0 (64-bit) . . . True Browser Core: Chrome version 125.0.0.0 (Engine: Blink)

Actual Behavior

True Operating System Core: Linux x86_64 . . . True Browser Core: Firefox

Screenshots

Browser Version

11.14.1 (64-bit)

Operating System

Linux (Debian SID)

Additional Context

Try Chameleon extension which works better: True Operating System Core: Unknown. Detection not supported or is blocked by browser setting(s)/extension(s). . . . True Browser Core: Chromium

[regularentropy]

The included user agent changer is obsolete. Please use extension.

[stilgarwolf]

I'm already using Chameleon