UPSIDER（悪意あるOSS経由の侵害）Data breach / unauthorized access incident
- Occurred on
- Unconfirmed
- Announced on
- April 10, 2026
- Severity
- SCompromise of deep personal data or usable credentials.
- Scale
- Unknown
- Main impact
- Unauthorized access occurred via an open-source software contaminated with a malicious program, and card payments and logins were suspended from April 1 3:40 to 10:49.
- Information involved
- User / member ID
- Cause / key point
- They attribute the unauthorized access to an open-source software that was contaminated with a malicious program.
- Industry
- IT & telecom
- Listing / capital
- Unlisted
- Last updated
- October 20, 2026
Is this incident worth paying attention to?
Written & reviewed
Reviewed byYutaro SasaoFounder & CEO, MediaLeap Inc.
CEO of MediaLeap Inc. Working on both sides of web advertising and web media since 2013; founded the company in May 2025.
Review scope: cross-checking against primary sources (official and government announcements), verifying claims stay within the facts, and checking source attribution。Last reviewed:
Written by:Leak Watch editorial team (AI-assisted drafts verified against sources by the editorial team) · Reviewer profile · Request a correction
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Attack method classification: Unauthorized access (method undisclosed)(Breached, but the technique was not identified or disclosed)
Read the Unauthorized access (method undisclosed) guide and national trends →