Korean IME composition causes editor crash (Firefox)

On Firefox with Windows 10 and Korean IME, specific key combination sequences during IME composition can cause the contenteditable editor to crash unexpectedly.

Problem Description

This issue occurs specifically when:

1. User is on Windows 10
2. Using Firefox browser
3. Using Korean IME (e.g., Microsoft IME)
4. Typing specific key sequences during IME composition

Crash Scenario

Based on the GitHub issue, the crash sequence is:

1. Enable Korean IME
2. Type ㅀ (press ‘f’, then ‘g’ on QWERTY keyboard)
3. Hit Enter to confirm composition
4. Press Ctrl+Shift+Home

Expected Behavior

• Editor should handle the key sequence normally
• No crash should occur
• IME composition should complete or be interrupted gracefully

Actual Behavior (Firefox Bug)

• Editor crashes: The contenteditable editor completely crashes
• JavaScript execution stops
• User must reload the page

Affected Browsers

• Firefox (Windows 10, with Korean IME) - Issue confirmed
• Chrome - Does NOT exhibit this crash
• Safari - Does NOT exhibit this crash

Affected Languages

• Korean IME (Microsoft IME on Windows)
• Similar issues may occur with other IMEs

Root Cause

Firefox’s IME handling appears to have a race condition or memory corruption when:

1. Processing specific key sequences (like Ctrl+Shift+Home) during active IME composition
2. The IME state management and editor DOM state get out of sync
3. Internal selection/range calculation crashes when conflicting operations occur

Workarounds

1. Prevent Ctrl+Shift+Home during composition:

   let isComposing = false;
   
   editor.addEventListener('compositionstart', () => {
     isComposing = true;
   });
   
   editor.addEventListener('keydown', (e) => {
     if (isComposing && e.ctrlKey && e.shiftKey && e.key === 'Home') {
       e.preventDefault();
       // Prevent problematic key combination during IME
     }
   });
   
   editor.addEventListener('compositionend', () => {
     isComposing = false;
   });

2. Try-catch around critical operations:

   editor.addEventListener('input', (e) => {
     try {
       // Handle input event
     } catch (error) {
       console.error('Input error:', error);
       // Recover gracefully
     }
   });

3. Use try-finally for cleanup:

   try {
     // IME operations
   } finally {
     // Always cleanup state
   }

References

• Draft.js Issue #2412: Korean IME crash - Original GitHub issue
• Stack Overflow: Draft.js not registering IME input - Related IME issues
• Firefox Bugzilla #1633399: Draft.js editor crash - Firefox crash reports
• Firefox Bugzilla #1739489: macOS Emoji crash - Related emoji crash
• Lightrun: Netlify CMS Hangul crash - Similar crash reports