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Positive Technologies Develops Dynamic Crawler for Single-Page Applications in PT BlackBox Scanner

Positive Technologies engineers have detailed the development of a dynamic crawler for their PT BlackBox DAST scanner to handle modern single-page applications built with frameworks such as React and Vue. The crawler must discover attack surface elements that only appear after user interactions because static parsing of initial DOM fails on SPAs where navigation occurs without URL changes. Key challenges include identifying interactive elements whose handlers are attached via JavaScript, detecting state changes after clicks or inputs, and managing combinatorial explosion of states caused by independent UI toggles. The team models the application as a labeled transition system and defines state equivalence using sets of 64-bit fingerprints of interactive elements rather than raw HTML similarity or URL values. This equivalence relation satisfies reflexivity, determinism from external observations, cheap hash-based comparison, slower growth than action count, and preservation of enabled actions across equivalent states. The approach allows the crawler to visit representatives of equivalence classes instead of every reachable state, keeping scans finite and practical within action budgets of several thousand interactions.