titlebar of box can "stick" out of titlebar in firefox - documentation problem?

[graf0]

Hi,

we have following code:

<div class="box">
  <div class="block titlebar">
    <strong>pike</strong>
  </div>
  <p>
    node is git
    <span class="float:right">
      <a href="#">ssh</a> |
      <a href="/systems/1/nodes/2">→ goto</a>
    </span>
  </p>
</div>

This is how it looks on Edge - as it should:

And this is how it looks on Firefox:

Notice how letter "p" goes just a little bit out of titlebar. There is also more shadow under it.