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.
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.