Horizon IT System is the Post Office's core transaction processing platform that records and reconciles subpostmasters' transactions.
Overview
Horizon IT System is the Post Office's core transaction processing platform that records and reconciles subpostmasters' transactions. It has a historically problematic data integrity track record, which makes it a focal point for cybersecurity concerns around data accuracy, upgrade risk, and auditability. The recent article ties Horizon-related services to a data breach caused by a botched website upgrade, highlighting ongoing security and operational risks in Horizon-enabled deployments.
Related Threat Clusters
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Post Office Reprimanded for Data Breach of Horizon IT Scandal Victims
The Information Commissioner’s Office (ICO) reprimanded Post Office Limited for a data breach that exposed personal information of 502 postmasters involved in the Horizon IT scandal. The breach occurred due to a human…
5 articles · Updated December 3, 2025
Recent Intelligence Reports
- Post Office avoids £1m fine over botched website upgrade data breach — Computerweekly · December 3, 2025