CVE-2026-125749: TaxHacker through 0.8.5 IDOR via Settings Server Actions userId

TaxHacker through 0.8.5 contains an insecure direct object reference vulnerability in app/(app)/settings/actions.ts that allows authenticated users to modify other users' data by supplying an arbitrary userId. Attackers can invoke Server Actions like deleteCategoryAction or editFieldAction with a victim's UUID to delete categories, clear transaction assignments, or alter LLM prompts.