The vulnerability stems from two key issues: 1) Insecure property access in template runtime that allowed prototype pollution via direct obj[name] access, and 2) Unsafe code generation in the compiler that didn't properly escape property names. The fixes in commits b6d3de7 and f058970 address these by introducing container.lookupProperty (which checks own properties) and JSON.stringify escaping respectively. The Snyk PoC demonstrates exploitation through prototype manipulation in strict mode, which would leverage these vulnerable code paths.