---
title: "Data breach at Cours Thalès"
description: "On 3 October 2026, a user on a cybercriminal forum claimed to have obtained about 40,000 billing records from Cours Thalès, a French school and higher-education preparation provider. The published samples link the name of the paying client and of the enrolled person to a postal address, a client ref"
canonical: https://inyourgeek.com/en/fuites-de-donnees/2026-10-03-cours-thales
type: fuite-de-donnees
author: "Sébastien Soulier"
publisher: "InYourGeek"
language: en
datePublished: 2026-10-03
dateModified: 2026-10-03
---
# Cours Thalès

Data breach — Moderate

On 3 October 2026, a user on a cybercriminal forum claimed to have obtained about 40,000 billing records from Cours Thalès, a French school and higher-education preparation provider. The published samples link the name of the paying client and of the enrolled person to a postal address, a client reference, an invoice number and date, and the payment amount, method, date and status. The author says an IDOR vulnerability was exploited; this is unconfirmed. The 40,000 figure counts records, not distinct people: one person can appear on several invoices, and the files cover both payers, often parents, and enrolled persons. Cours Thalès has not issued a statement so far.

These data allow a malicious third party to link an enrolled person to their payer and postal address, and to use real billing details to make fraudulent letters or messages credible.

| Fact | Value |
| --- | --- |
| Disclosed on | October 3, 2026 |
| Incident dated | October 3, 2026 |
| Sector | Education |
| Country | France |
| Cause | Undisclosed |
| Severity | Moderate |
| Status | Reported |

## Exposed data

- Full name
- Postal address
- Customer ID
- Order history

## What you can do

- You can ask the organisation exactly what was exposed about you (right of access), and complain to the DPA if no answer comes within a month.

## Sources

- [Cours Thalès](https://frenchbreaches.com/alertes/cours-thal-s-musgbt3pvmwpqeg5v6) — FrenchBreaches
- [Cours Thalès : fuite de données revendiquée visant 18 800 personnes](https://fuitesinfos.fr/article/2026-10-03-cours-thales) — Fuites Infos
- [Cours Thalès : 40 070 données de facturation exposées après une faille IDOR](https://www.cyberattaque.org/cyberattaque-cours-thales-40-070-donnees-de-facturation-exposees-apres-une-faille-idor/) — Cyberattaque.org

_Entry built from the cited sources after a corroboration check, then reviewed before publication._

---

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