Bug 508643 - Conflict between Firefox 142 and customised window decorations causing consistent crash
Summary: Conflict between Firefox 142 and customised window decorations causing consis...
Status: RESOLVED UPSTREAM
Alias: None
Product: Breeze
Classification: Plasma
Component: window decoration (other bugs)
Version First Reported In: 6.4.4
Platform: Fedora RPMs Linux
: NOR crash
Target Milestone: ---
Assignee: Plasma Bugs List
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2025-08-23 12:36 UTC by jw_bugzilla
Modified: 2025-08-25 16:07 UTC (History)
2 users (show)

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Description jw_bugzilla 2025-08-23 12:36:08 UTC 
SUMMARY
When KDE window decorations are customised to appear on both ends of the titlebar, Firefox 142 crashes on launch.

STEPS TO REPRODUCE
1. Go to settings -> colours and themes -> window decorations -> configure titlebar buttons.
2. Ensure close, minimise, and maximise buttons appear on both ends (left and right) of the titlebar. Save changes.
3. Attempt to launch Firefox 142.

OBSERVED RESULT
Firefox immediately crashes. Running in terminal produces an error:

/usr/include/c++/15/array:210: constexpr std::array<_Tp, _Nm>::value_type& std::array<_Tp, _Nm>::operator[](size_type) [with _Tp = HeaderBarButtonType; long unsigned int _Nm = 3; reference = HeaderBarButtonType&; size_type = long unsigned int]: Assertion '__n < this->size()' failed.


EXPECTED RESULT
Firefox launches normally

SOFTWARE/OS VERSIONS
KDE Plasma Version: 6.4.4
KDE Frameworks Version: 6.17.0
Qt Version: 6.9.1

ADDITIONAL INFORMATION
Also submitted as a bug for Firefox at https://bugzilla.mozilla.org/show_bug.cgi?id=1984823
Comment 1 jw_bugzilla 2025-08-25 16:07:53 UTC 
Resolved as an issue with Firefox in the previously linked thread