Sonar's new JS/TS engine: Tracing meaning, not syntax, to hunt down real vulnerabilities

A theory-grounded static-analysis engine using abstract interpretation identified a low-severity reflected HTML injection in FlowiseAI’s unauthenticated OAuth2 callback, illustrating how semantic data-flow analysis can trace tainted values through real TypeScript code more reliably than syntax-based rules or shallow call-graph approaches. The issue allowed the request’s state parameter to pass through an Express handler, template interpolation, cross-file function calls, an options object, destructuring, and a long HTML template before reaching Express’s res.send() response sink. Although global sanitize-html middleware blocked scripts and event handlers, permitted anchor tags could still render attacker-controlled links on FlowiseAI’s domain, creating a phishing risk rather than enabling script execution. The example emphasizes that accurate analysis of production JavaScript and TypeScript requires framework-aware source and sink modeling, import resolution, argument-to-parameter binding, object and destructuring tracking, return propagation, and interpolation-level precision. FlowiseAI independently fixed the issue by explicitly HTML-escaping template values before publication.

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