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chromium/third_party/blink/web_tests/fast/forms/validation-bubble-appearance-escape.html 

<!DOCTYPE html>
<input pattern="\d{4}" title="Please specify four digits." value="abc" style="position:absolute; top: 100px">
<script>
document.querySelector('input').setCustomValidity('<script>');
document.querySelector('input').reportValidity();
</script>