[xsl] XSL Injection, is it possible?

["G. T. Stresen-Reuter" <tedmasterweb@xxxxxxx>]

Hi,

I have a web-based CMS in which all the data is stored in an XML file. 
I use XSL extensively. I take user input and insert it into the XML 
file in several different places.

Currently my sanitizing function just escapes <, >, ', and " in the 
input but I was wondering if anyone knows of other vectors by which 
attackers can enter. Are these characters recognized by the XSLT engine 
if they are hex or unicode encoded?

Thanks in advance and I hope this hasn't been covered elsewhere (I 
haven't been able to find anything on it).

Ted Stresen-Reuter