Trivial Description
I recently started using XStream for development not related to Struts 2, and found that the version being used is 1.2.2, which was released in May of 2007 [1][2]. I upgraded to 1.4.2, the latest[3], and haven't had any issues with Struts although I have not exhaustively tested and certainly haven't run any Struts core unit tests. Having a newer version would make it easier to utilize within the same web app. for which I'm running Struts 2.
[1] http://repo1.maven.org/maven2/com/thoughtworks/xstream/xstream/1.2.2/
[2] http://xstream.codehaus.org/changes.html
[3] http://xstream.codehaus.org/download.html