High Severity
The visitHistory field is a Stack<string> class instance persisted to sessionStorage via pinia-plugin-persistedstate. There's no custom serializer or hydration hook. When the page reloads, JSON.parse(JSON.stringify(stack)) produces a plain object {dedup, items, maxSize} that lacks all Stack methods (push, pop, remove, retain, etc.) and the size getter. Pinia's $patch replaces the Stack instance with this plain object, so subsequent calls like this.visitHistory.push(...) will throw a TypeError.
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