Vega Cross-Site Scripting (XSS) via expressions abusing toString calls in environments using the VEGA_DEBUG global variable

Impact Applications meeting 2 conditions are at risk of arbitrary JavaScript code execution, even if "safe mode" expressionInterpreter is used. 1. Use vega in an application that attaches vega library and a vega.View instance similar to the Vega Editor to the global window 2. Allow user-defined...