Was HMH (hmhco.com) hit by ransomware?

HMH (hmhco.com) was listed by the shinyhunters ransomware operation (United States), and stolen data was published on the group's leak site. Darkfield tracks this disclosure with the original leak post, screenshot and group context.

Who is the shinyhunters ransomware group?

shinyhunters is a ransomware operator tracked by Darkfield. See the full operator dossier for its known victims, sectors targeted, IOCs and leak-site infrastructure.

What data was leaked in the HMH (hmhco.com) breach?

shinyhunters published data attributed to HMH (hmhco.com). Darkfield captured the leak post and a screenshot of the listing.

Ransomware victim disclosure

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Houghton Mifflin Harcourt

listed as HMH (hmhco.com) · Claimed by Shinyhunters · listed 9 months ago

Age

since listed · data leaked

Status timeline

ListedOct 3, 2025
Data leakeddate unknown

At a glance

Group: Shinyhunters
Status: Data leaked
Country: United States
Sector: Education
Listed on leak site: Oct 3, 2025

About the victim

AI dossier — public-source company profile

Houghton Mifflin Harcourt (HMH) is a major U.S.-based K-12 learning company headquartered in Boston, Massachusetts, providing core curriculum, supplemental programs, assessments, and instructional technology across literacy, math, science, and other subjects. The company serves schools and educators in over 150 countries with both print and digital learning solutions. HMH also publishes well-known trade, reference, and children's book titles.

Industry: K-12 Educational Publishing & EdTech
Address: 125 High Street, Boston, MA 02110, United States
Employees: 5000-10000
Founded: 1832

Attack summary

Severity: high — ShinyHunters is a prolific data-exfiltration group with a track record of large-scale credential and PII theft; the 'data_published' status indicates data has been released publicly. HMH operates digital learning platforms serving millions of K-12 students and educators, meaning any exfiltrated data could include student PII, account credentials, or educational records potentially covered by FERPA — regulated sensitive data at significant scale.

ShinyHunters claims to have obtained data from HMH and has published it ('data_published' status), though the leak post provides no explicit description of encryption or specific exfiltration details. No ransom amount was stated and no data size or proof file count was advertised.

high

Data the group says was taken

AI dossier — extracted from the leak post

Unspecified exfiltrated company data

Original description

AI-summarised, not from the leak post

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.

Sources

Victim sitehmhco.com
Leak posthttps://breachforums.hn//hmhco.html

Source

Indexed 9 months ago

This page surfaces a public ransomware disclosure indexed by Darkfield. Original posts come from the operator's own leak site; we cross-check against ransomware.live, RansomLook and RansomWatch where applicable. Share this URL freely.

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Disclosure context

About shinyhunters

Based on the limited publicly available information, shinyhunters appears to be a recently emerged ransomware group first observed in October 2025, primarily motivated by financial gain through extortion activities targeting organizations across multiple sectors. The group's origin and potential affiliations remain unclear due to their recent emergence, and there is insufficient public documentation to determine whether they operate as a Ransomware-as-a-Service model or as an independent entity. Their attack methodology and specific technical capabilities have not been extensively documented by major threat intelligence firms, though their targeting pattern suggests a broad opportunistic approach rather than sector-specific specialization. The group has reportedly victimized approximately 77 organizations, with primary targeting focused on the United States, France, Japan, Germany, and Australia, showing particular interest in consumer services, technology, financial services, transportation and logistics, and education sectors. Given the group's very recent emergence in late 2025, there are no widely reported major campaigns or high-profile incidents documented by established security research organizations, and no known law enforcement actions have been publicly reported against this group. The current operational status of shinyhunters remains active based on available reporting, though comprehensive threat intelligence profiles from major security firms like Mandiant, CrowdStrike, or government agencies have not yet been published due to the group's recent appearance in the threat landscape. The group has been linked to 139 public disclosures across our corpus. First observed on a leak site on October 3, 2025; most recent post July 15, 2026. The operation is currently active.

Timeline of this disclosure

October 3, 2025HMH (hmhco.com) listed by shinyhunterson the group's public leak site

Other recent disclosures by shinyhunters

shinyhunters has been linked to 139 public victims on Darkfield. A sample of the most recent:

See the full shinyhunters dossier →

Sector and geography

This disclosure adds to ransomware activity in the Education sector, which has 1,082 disclosures indexed across all operators we track. Geographically, HMH (hmhco.com) is reported in United States, a country with 11,033 ransomware disclosures in our corpus.

If your organisation is affected

A listing by shinyhunters means HMH (hmhco.com) appeared on a ransomware extortion site and data attributed to it has been published. If this is your organisation, or a supplier you depend on, the priority is to confirm the intrusion and contain it before the window to act closes.

Engage your incident-response team and preserve forensic evidence before remediating — do not wipe affected systems first.
Force a password reset and revoke active sessions for exposed accounts; rotate any credentials, API keys or certificates that may have been in the stolen data.
Assess regulatory notification duties (GDPR, NIS2, sector regulators) — many carry a 72-hour reporting clock from awareness.
Report the incident to your national CERT, CISA (United States), as required for your jurisdiction.
Monitor for the data appearing on shinyhunters's leak site and across paste and breach channels, and brief downstream partners who may be exposed through you.

How we know this. Darkfield monitors public ransomware leak sites continuously, archiving every new disclosure and the data later released against the victim. Each entry on this page is sourced from the operator's own publication and cross-checked against complementary OSINT feeds (RansomLook, ransomware.live, RansomWatch). We do not collect or host stolen data — only the metadata, timestamps and screenshots needed to make the public disclosure searchable and accountable. Records here are corrected when the original post is edited, retracted, or merged with another disclosure.