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Houghton Mifflin Harcourt Company

shinyhunters

This record tracks a ransomware attack claimed by the shinyhunters group against Houghton Mifflin Harcourt Company. It collects the publicly disclosed attack details — sector, location and timeline — as published on the operator's leak site and indexed by Breach House.

Window Zero

EXPOSURE GAP

Window Zero is the time the breach stayed in the open before anyone said so — the gap between when the attack was first discovered on the operator's leak site (t1) and when it was publicly disclosed (t2). The wider this window, the longer victims, staff and customers were exposed with no warning.

114days open
t1 · Published t2 · Pending
May 09, 2026Not disclosed yet
Country
United States
Business Category
Education
Employees
51-100
Discovered
2026-05-09
Published
May 09, 2026
Disclosed / Notified
Not disclosed yet
Victim ID
W54WZem7pJuB

Attack Summary

Your data was compromised in several of our campaigns throughout the past few months. We urge you to engage with us, it is in your best interests. This is a final warning to reach out by 12 May 2026 before we leak along with several annoying (digital) problems that'll come your way. Make the right decision, don't be the next headline. | Updated: 9 May 2026 | Warning: FINAL WARNING PAY OR LEAK

Leak Screenshots

SAMPLE

Proof-of-breach screenshots the operator posted from the stolen data. Previews are redacted and locked — the originals are available on HaveIBeenRansom.

file_tree.png
finance_2024.xlsx
passport_scan.jpg
contract_signed.pdf
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Dark Web Exposure

Findings for hmhco.com — indexed by HaveIBeenRansom.
7,511
found in Infostealer logs
2,791+
found in Traditional breaches
209+
found in Ransomware leaks
Apollo.io DB 816millions.rar
Database World ROC · breach
••• emails
pureincubation-com.7z.001
Database World ROC · breach
••• emails
limeleads_breach.7z
TheUnderground - Reborn · breach
••• emails
@BreachedData1 LinkedIn 2021-23 Cleaned.7z.001
Database World ROC · breach
••• emails
VerificationsIO_BF.7z.011
Kedr | Forum 🪾 · breach
••• emails
play · ransomware
••• emails
play · ransomware
••• emails
Database World ROC · breach
••• emails
+ 17 more leak sources locked
Leak volumes are locked
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