Steps to reproduce the issue

I have found that while websites are using Joomla-software there appears to be a bug which makes it appear that the books published by DeLex are freely accessible for visitors of numerous websites (list below). We are receiving 3 to 5 announcements per day of our titles offered via Joomla-instructed websites. DeLex is a publishing agency, however, and the titles that are appearing free of charge aren’t free to use or to download.

Expected result

No appearance of any of our material for download

Actual result

The ebooks can not be downloaded, but leads you to other obscure websites; which leads to more obscure websites and leads to no downloads by the way...

System information (as much as possible)

Additional comments

Some references, but we get multiple messages per day...
1. http://www.cnenov.com/index.php/?option=com_k2&view=itemlist&task=user&id=15037.html (according to the source code it is JOOMLA-based)

1. http://fbroker.com.ua/?option=com_k2&view=itemlist&task=user&id=17025.html
   (according to the source code it has a JOOMLA-theme)

2. http://www.januszkurtyka.info/?option=com_k2&view=itemlist&task=user&id=34436.html
   (according to the source code it has a JOOMLA-generator: "

3. http://www.viviaranova.it/aranova/?option=com_k2&view=itemlist&task=user&id=9490.html
   according to the source code it has a JOOMLA-generator: "

4. http://www.luisaquaglia.it/?option=com_k2&view=itemlist&task=user&id=105873.html
   according to the source code it has a JOOMLA-generator and CSS.

Note that the URLs all end with "?option=com_k2&view=itemlist&task=user&id=".

Addition to the previous list of the last 3 days:
http://www.seicsa.mx/?option=com_k2&view=itemlist&task=user&id=31368.html

http://www.salaaniello.com/?option=com_k2&view=itemlist&task=user&id=89362.html

http://www.robbertcharoe.nl/?option=com_k2&view=itemlist&task=user&id=31287.html

http://www.radiolegal.com.mx/?option=com_k2&view=itemlist&task=user&id=996246.html
http://okzbd.com/rubaiyat/?option=com_k2&view=itemlist&task=user&id=34004.html

http://www.vhfilm.vn/index.php/component/k2/author/16276.html?Itemid=0

http://regencylimoservices.com/?option=com_k2&view=itemlist&task=user&id=238506.html

http://www.trenirovka365.ru/?option=com_k2&view=itemlist&task=user&id=248162.html

http://www.studio-moda.it/?option=com_k2&view=itemlist&task=user&id=90312.html

http://cantral4u.com/?option=com_k2&view=itemlist&task=user&id=16490.html

and so on...