My WordPress blog creates many dynamic URLs, which creates a content duplication issue for my website. As each page gets a different live URL, it’s being considered as a duplicate page.
Why are dynamic URLs getting indexed and creating this content duplication issue?
This issue is not necessarily with wordpress, rather Google allows you to exclude specific url parameters.
So you should exclude the session_id parameter, and possible others… have a look around the Craw->url parameters section of you webmaster account. There are a number of different options, depending on what the roles of your parameters are.