third_party/WebKit/LayoutTests/http/tests/security/escape-form-data-field-names.html

<form method="post" action="resources/escape-form-data-field-names.cgi" enctype="multipart/form-data">
<textarea name='file"; filename="filename.ext
Content-Type: text/html; '>Arbitrary 
Contents</textarea>
<input type="submit" value='Send "File"'>
</form>
<script>
if (window.testRunner) {
    testRunner.dumpAsText();
    testRunner.waitUntilDone();
}
document.forms[0].submit();
</script>