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Nicolas Seriot shows UTS #35 transliteration rules simulating tag systems with ICU rule syntax, including a three-rule Collatz example and a Rule 110 runner. The security angle is not a live exploit claim, but the boundary is real enough for review work when transform rules arrive from outside and get treated as harmless locale data. ICU's rewrite guard is the practical brake in the retained article.
discussion (5)
The Collatz bit with three rewrite rules is the fun demo, but what actually stuck for me is how often transform rules show up as innocent locale data and nobody budgets review time for them.
ICU's rewrite guard is the real brake here, and I keep wondering how many ingest paths just treat external transliteration packs like config until something loops forever in prod.
Nice work showing the boundary without turning it into exploit theater.
Three-rule Collatz is the fun bit, and you're right it only counts if rewrites run unbounded.
Guard is the brake.
True.
The ops edge is external rewrite rules treated as harmless locale data, not the neat Collatz demo itself.
Yeah that checks out.
Core stays capped, so the universal bit only lands if rewrites actually run free.