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>
    <allimages>
      <img name="En-5.0-images-vpn-zentyal_as_client.png" timestamp="2017-04-18T17:47:29Z" user="Admin" url="https://wiki.zentyal.org/images/e/e6/En-5.0-images-vpn-zentyal_as_client.png" descriptionurl="https://wiki.zentyal.org/wiki/File:En-5.0-images-vpn-zentyal_as_client.png" ns="6" title="File:En-5.0-images-vpn-zentyal as client.png" />
      <img name="En-5.0-images-vpn-zentyal_client_conf.png" timestamp="2017-04-18T17:44:56Z" user="Admin" url="https://wiki.zentyal.org/images/b/b1/En-5.0-images-vpn-zentyal_client_conf.png" descriptionurl="https://wiki.zentyal.org/wiki/File:En-5.0-images-vpn-zentyal_client_conf.png" ns="6" title="File:En-5.0-images-vpn-zentyal client conf.png" />
      <img name="En-5.0-images-vpn-zentyal_client.png" timestamp="2017-04-18T17:42:51Z" user="Admin" url="https://wiki.zentyal.org/images/2/2d/En-5.0-images-vpn-zentyal_client.png" descriptionurl="https://wiki.zentyal.org/wiki/File:En-5.0-images-vpn-zentyal_client.png" ns="6" title="File:En-5.0-images-vpn-zentyal client.png" />
      <img name="En-5.0-images-vpn-two-offices.png" timestamp="2017-04-18T17:41:07Z" user="Admin" url="https://wiki.zentyal.org/images/e/ef/En-5.0-images-vpn-two-offices.png" descriptionurl="https://wiki.zentyal.org/wiki/File:En-5.0-images-vpn-two-offices.png" ns="6" title="File:En-5.0-images-vpn-two-offices.png" />
      <img name="En-5.0-images-vpn-03-vpn-client.png" timestamp="2017-04-18T17:39:07Z" user="Admin" url="https://wiki.zentyal.org/images/5/54/En-5.0-images-vpn-03-vpn-client.png" descriptionurl="https://wiki.zentyal.org/wiki/File:En-5.0-images-vpn-03-vpn-client.png" ns="6" title="File:En-5.0-images-vpn-03-vpn-client.png" />
      <img name="En-5.0-images-vpn-client_bundle.png" timestamp="2017-04-18T17:37:09Z" user="Admin" url="https://wiki.zentyal.org/images/c/cf/En-5.0-images-vpn-client_bundle.png" descriptionurl="https://wiki.zentyal.org/wiki/File:En-5.0-images-vpn-client_bundle.png" ns="6" title="File:En-5.0-images-vpn-client bundle.png" />
      <img name="En-5.0-images-vpn-advertised.png" timestamp="2017-04-18T17:35:15Z" user="Admin" url="https://wiki.zentyal.org/images/2/2b/En-5.0-images-vpn-advertised.png" descriptionurl="https://wiki.zentyal.org/wiki/File:En-5.0-images-vpn-advertised.png" ns="6" title="File:En-5.0-images-vpn-advertised.png" />
      <img name="En-5.0-images-vpn-vpn_gateway.png" timestamp="2017-04-18T17:33:12Z" user="Admin" url="https://wiki.zentyal.org/images/7/72/En-5.0-images-vpn-vpn_gateway.png" descriptionurl="https://wiki.zentyal.org/wiki/File:En-5.0-images-vpn-vpn_gateway.png" ns="6" title="File:En-5.0-images-vpn-vpn gateway.png" />
      <img name="En-5.0-images-vpn-vpnnat.png" timestamp="2017-04-18T17:31:15Z" user="Admin" url="https://wiki.zentyal.org/images/8/85/En-5.0-images-vpn-vpnnat.png" descriptionurl="https://wiki.zentyal.org/wiki/File:En-5.0-images-vpn-vpnnat.png" ns="6" title="File:En-5.0-images-vpn-vpnnat.png" />
      <img name="En-5.0-images-vpn-02-vpn-server.png" timestamp="2017-04-18T17:28:49Z" user="Admin" url="https://wiki.zentyal.org/images/9/98/En-5.0-images-vpn-02-vpn-server.png" descriptionurl="https://wiki.zentyal.org/wiki/File:En-5.0-images-vpn-02-vpn-server.png" ns="6" title="File:En-5.0-images-vpn-02-vpn-server.png" />
    </allimages>
  </query>
  <query-continue>
    <allimages aistart="2017-04-18T17:27:12Z" />
  </query-continue>
</api>