This is a whitepaper that discusses a reflective cross site scripting issue in *.adspecs.yahoo.com due to sessvars.js not filtering before performing an eval.
You can download it from the following link: https://packetstormsecurity.com/files/download/119560/domsday-yahoo.pdf
Source: https://packetstormsecurity.com/files/119560/DOMSDAY-Analyzing-A-DOM-Based-XSS-In-Yahoo.html