mod_http_oauth2: Reduce authorization code validity time to 2 minutes RFC 6749 states > A maximum authorization code lifetime of 10 minutes is RECOMMENDED. So 15 minutes was way too long. I was thinking 5 minutes at first but since this should generally be instant, I settled on 2 minutes as a large guesstimate on how slow it might be on slow links.

<tr>
  <th>What is {x} {op} {y}?</th><td>
    <input name="captcha_challenge" type="hidden" value="{challenge}">
    <input name="captcha_reply" pattern="[0-9]+" required type="number">
  </td></tr>