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HTML is good for debugging, but probably is not suitable for your application.
See complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query>
    <userinfo id="0" name="18.118.150.80" anon="" blockedby="" blockreason="כתובת ה־IP שלכם רשומה ככתובת פרוקסי פתוחה ב־DNSBL שאתר זה משתמש בו.">
      <groups>
        <g>*</g>
        <g>autoconfirmed</g>
      </groups>
      <rights>
        <r>createaccount</r>
        <r>read</r>
        <r>edit</r>
        <r>createpage</r>
        <r>createtalk</r>
        <r>writeapi</r>
      </rights>
    </userinfo>
  </query>
</api>