This whitepaper focuses on a method of stealing data as a client side script’s identifier (variable or function name). The author describes these attack techniques / browser vulnerabilities and then discuss countermeasures for these issues.
You can download it from the following link: https://packetstormsecurity.com/files/download/131430/xssi.pdf
Source: https://packetstormsecurity.com/files/131430/Identifier-Based-XSSI-Attacks.html