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MacOS 15.8.1 kills Firefox & Thunderbird at start

Firefox Launch failure
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I need help with MacOS Sequoia 15.8.1 (24H32).

Since yesterday’s update to 15.8, Firefox and Thunderbird no longer work—regardless of the build or version. The system immediately terminates the apps with this message in the Apple error report:

System Integrity Protection: enabled Crashed Thread: 0 MainThread Dispatch queue: com.apple.main-thread Exception Type: EXC_GUARD (SIGKILL) Exception Codes: GUARD_TYPE_MACH_PORT Exception Codes: 0x0000000000000203, 0x0000000000000000 Termination Reason: Namespace GUARD, Code 2305843146652647939

Translated with DeepL.com (free version)

I need help with MacOS Sequoia 15.8.1 (24H32). Since yesterday’s update to 15.8, Firefox and Thunderbird no longer work—regardless of the build or version. The system immediately terminates the apps with this message in the Apple error report: System Integrity Protection: enabled Crashed Thread: 0 MainThread Dispatch queue: com.apple.main-thread Exception Type: EXC_GUARD (SIGKILL) Exception Codes: GUARD_TYPE_MACH_PORT Exception Codes: 0x0000000000000203, 0x0000000000000000 Termination Reason: Namespace GUARD, Code 2305843146652647939 Translated with DeepL.com (free version)

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