Google will use URL parameters to crawl anything it can and you allow to find in a website. So this is an expected behavior for sites that have dynamically created pages.
These days Google is very smart and can identify the correct url for a page and will present this to any potential searcher. It really manages this pretty well.
In general if you are concerned about any duplicate content penalty for a case like this, you shouldn't. In a brief, Duplicate content penalty arrives when a website is copying content from others. This is what Google considers as duplicate content.
The only negative effect you might have, is a possible lose of page-rank for the page in question, because of the content existing in more than 1 pages.
Of course you can instruct Google to not index this page. Either by using Canonical URLs (should be your first option), either by Blocking it in the Robots.txt, or by tweaking the URLs parameters of Google crawler in Google Webmasters Tools.
Read also this answer, that explains the nature of dynamic pages: How to deal with Duplicated Content / URLs in Joomla?