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Osaka High Court: Teams mis-invite of about 6,000 accounts exposed usernames and emails to each other

On Aug 27, 2026 a case Teams team wrongly added ~3,500 external and ~2,500 staff accounts; invitees could see each other’s usernames/emails until same-day deletion. Court notices index dates the apology Sep 4.

Last updated: 2026-11-09

Overview

“About 3,500” and “about 2,500” → blank (not summed).

Timeline

  1. Occurred
  2. Discovered
  3. Disclosed

Organization response

Per the notice, the organisation investigated and contained the incident, notified individuals and offered monitoring or protective resources.

What you can do

Be wary of emails, SMS or calls impersonating the organisation; do not open links or attachments or enter passwords or card details. Change reused passwords on other services.

Sources

  1. お知らせ（令和8年9月4日掲載）大阪高等裁判所 · 2026-11-09
  2. 大阪高等裁判所における特定の事件に係るMicrosoft Teamsのチーム作成の誤りについて（お詫び）大阪高等裁判所 · 2026-11-09

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