Short for data source object, a DSO is an embedded ActiveX control that enables an HTML document to display information from an external XML data source or another page web page. For example, a DSO could be used to add and interactive map or weather radar to your site from another.
Note: Internet Explorer 4.0 and later is required for the use of DSOs.
Known DSO exploit
A DSO exploit was discovered by GreyMagic Software on February 25, 2002, that dynamically inserts HTML without using any active scripting. This hole in Internet Explorer can enable a malicious user to execute a program from a browser window, allowing them to install unwanted software onto your computer.