Korean IME composition cancelled by paste operation in Firefox

Phenomenon

When composing Korean text with IME in a contenteditable element, pasting content (Ctrl+V) cancels the active composition and loses the composed text. The pasted content may also be inserted in an unexpected position.

Reproduction example

1. Focus the editable area.
2. Activate Korean IME.
3. Start composing Korean text (e.g., type “한글”).
4. Press Ctrl+V to paste content before completing composition.

Observed behavior

• The compositionend event fires with incomplete data
• The composed text is lost
• Pasted content is inserted, possibly in wrong position
• The sequence of paste, compositionend, and input events may be inconsistent

Expected behavior

• Composition should complete before paste occurs, or paste should be queued
• Composed text should not be lost
• Pasted content should be inserted in the correct position
• Event sequence should be predictable and consistent

Browser Comparison

• Firefox: Paste may cancel composition
• Chrome: May have different paste behavior during composition
• Edge: Similar to Chrome
• Safari: Not applicable on Windows

Notes and possible direction for workarounds

• Prevent paste during active composition
• Wait for composition to complete, then allow paste
• Handle paste events carefully during composition