When you open the list of options, the footer is affected and has its position changed.
Code in the fiddle
One solution would be to put the dropdown open up, so just put the class dropup
on the div
that involves the dropdown:
<div class="input-group-btn dropup">
<button type="button" class="btn btn-primary dropdown-toggle" id="btn-dropdown-uf" data-toggle="dropdown">
Selecione <span class="caret"></span>
</button>
<ul class="dropdown-menu dropdown-menu-right dropdown-high" aria-labelledby="btn-dropdown-uf" role="menu">
<li><a href="#">AC</a></li>
<li><a href="#">AL</a></li>
<li><a href="#">AP</a></li>
<li><a href="#">AM</a></li>
<li><a href="#">BA</a></li>
<li><a href="#">CE</a></li>
<li><a href="#">DF</a></li>
<li><a href="#">ES</a></li>
<li><a href="#">GO</a></li>
<li><a href="#">MA</a></li>
<li><a href="#">MT</a></li>
<li><a href="#">MS</a></li>
<li><a href="#">MG</a></li>
<li><a href="#">PA</a></li>
<li><a href="#">PB</a></li>
<li><a href="#">PR</a></li>
<li><a href="#">PE</a></li>
<li><a href="#">PI</a></li>
<li><a href="#">RJ</a></li>
<li><a href="#">RN</a></li>
<li><a href="#">RS</a></li>
<li><a href="#">RO</a></li>
<li><a href="#">RR</a></li>
<li><a href="#">SC</a></li>
<li><a href="#">SP</a></li>
<li><a href="#">SE</a></li>
<li><a href="#">TO</a></li>
</ul>
</div>