HMH (hmhco.com)
shinyhuntersThis record tracks a ransomware attack claimed by the shinyhunters group against HMH (hmhco.com). 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 GAPWindow 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.
Attack Summary
[AI generated] HMH, or Houghton Mifflin Harcourt, is a long-established publishing company specializing in educational content. They provide a variety of instructional technology, assessments, and other learning materials to schools in over 150 countries. The company also publishes a number of well-known trade and reference works, alongside children's books. Their goal is to foster a lifelong love of learning in every individual they serve.
Leak Screenshots
SAMPLEProof-of-breach screenshots the operator posted from the stolen data. Previews are redacted and locked — the originals are available on HaveIBeenRansom.