You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information.
<?xml version="1.0"?>
<api>
  <query-continue>
    <allusers aufrom="Z377 buy clavamox online cheap" />
  </query-continue>
  <query>
    <allusers>
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      <u userid="3721" name="Ybmk buy cardura online cheap" />
      <u userid="3920" name="Yenm buy zestoretic online cheap" />
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      <u userid="3726" name="Yytl buy meclizine online cheap" />
      <u userid="67" name="Yzbclg" />
    </allusers>
  </query>
</api>