mod_http_oauth2: Keep authorization codes in memory instead of storage Seems excessive to have them in persistent storage for such a short time. Prevents them from leaking in case they never get cashed out.

<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>