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Cyber Threat
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Ransomware victim Education

Houghton Mifflin Harcourt Company

Listed by Shinyhunters on · organisation based in United States

hmhco.com

Disclosed
May 9, 2026
Leak-site listing date
Threat group
Shinyhunters
168 victims listed
Country
United States
#1 most targeted
Sector
Education

ThreatAI analysis

Compiled from this incident record and the threat intelligence profile for Shinyhunters. Figures and technique mappings are quoted from the source data, not inferred.

About the Shinyhunters group

ShinyHunters is a financially motivated data-theft and extortion group active since 2020, responsible for high-profile breaches including Ticketmaster (via Snowflake) and PowerSchool; by 2025 they launched a RaaS offering called "shinysp1d3r," and in August 2025 French authorities arrested four members. Shinyhunters has listed 161 victims since April 2024.

How Shinyhunters is documented to operate

Data from Information Repositories T1213 Collection

Adversaries may leverage information repositories to mine valuable information. Information repositories are tools that allow for storage of information, typically to facilitate collaboration or information sharing between users, and can store a wide variety of data that may aid adversaries in further objectives, such as Credential Access, Lateral Movement, or Defense Evasion, or direct access to the target information. Adversaries may also abuse external sharing features to share sensitive documents with recipients outside of the organization (i.e., Transfer Data to Cloud Account).

Mitigations: User Training, Out-of-Band Communications Channel, User Account Management, Multi-factor Authentication, Software Configuration, Audit

MITRE ATT&CK reference
Exfiltration Over Web Service T1567 Exfiltration

Adversaries may use an existing, legitimate external Web service to exfiltrate data rather than their primary command and control channel. Popular Web services acting as an exfiltration mechanism may give a significant amount of cover due to the likelihood that hosts within a network are already communicating with them prior to compromise. Firewall rules may also already exist to permit traffic to these services. Web service providers also commonly use SSL/TLS encryption, giving adversaries an added level of protection.

Mitigations: Restrict Web-Based Content, Data Loss Prevention

MITRE ATT&CK reference
Data Encrypted for Impact T1486 Impact

Adversaries may encrypt data on target systems or on large numbers of systems in a network to interrupt availability to system and network resources. They can attempt to render stored data inaccessible by encrypting files or data on local and remote drives and withholding access to a decryption key. This may be done in order to extract monetary compensation from a victim in exchange for decryption or a decryption key (ransomware) or to render data permanently inaccessible in cases where the key is not saved or transmitted.

Mitigations: Data Backup, Behavior Prevention on Endpoint

MITRE ATT&CK reference

MITRE ATT&CK techniques attributed to Shinyhunters across its recorded activity, not a finding about how Houghton Mifflin Harcourt Company was reached.

Vulnerabilities Shinyhunters is recorded exploiting

3 of these 3 are in the CISA Known Exploited Vulnerabilities catalog, 2 of them recorded by CISA as used in ransomware campaigns. CVEs attributed to Shinyhunters across its reported activity. There is no indication that any of these was involved in the Houghton Mifflin Harcourt Company incident — the source data does not record an entry point.

Incident analysis

Houghton Mifflin Harcourt Company was listed by Shinyhunters ransomware, a group with 168 victims recorded in this database. The listing appeared on the group's leak site on May 9, 2026.

Houghton Mifflin Harcourt Company is based in United States and operates in the Education sector. United States ranks #1 worldwide for ransomware disclosures, with 10,166 victims in this database.

Sector context. Educational institutions often have under-resourced IT security teams and hold large amounts of student and faculty personal data, making them attractive targets for ransomware groups.

Shinyhunters typically follows a double extortion model: data is exfiltrated from the victim's systems before files are encrypted, so the victim faces two demands at once — pay to restore access, and pay to keep stolen data unpublished. The leak site, where this listing appeared, is the lever for the second demand.

Source. Public leak-site disclosures aggregated via the ransomware.live API. The disclosure date is when the listing was published, which can differ from the date of compromise. This site does not publish or link to stolen data. Last updated .

Frequently asked questions

Was Houghton Mifflin Harcourt Company attacked by ransomware?

Yes. Houghton Mifflin Harcourt Company was listed as a victim of the Shinyhunters ransomware group on May 9, 2026. The organisation is based in United States and operates in the Education sector. The disclosure appeared on the group's dark web leak site.

Which ransomware group attacked Houghton Mifflin Harcourt Company?

Houghton Mifflin Harcourt Company was attacked by Shinyhunters ransomware. Shinyhunters is one of the most active ransomware groups, having claimed 168 victims globally. The group typically employs a double-extortion model: encrypting the victim's files and threatening to publish stolen data.

When did the Houghton Mifflin Harcourt Company ransomware attack occur?

The ransomware attack on Houghton Mifflin Harcourt Company was disclosed on May 9, 2026. This date reflects when the victim was published on the threat group's leak site, which may differ from the actual date of initial compromise.

What data was stolen in the Houghton Mifflin Harcourt Company ransomware attack?

The specific data stolen from Houghton Mifflin Harcourt Company has not been independently verified by this platform. Ransomware groups typically exfiltrate data before encrypting systems and use the threat of publication to pressure victims. As a Education organisation, Houghton Mifflin Harcourt Company likely held student and faculty personal data and academic records.

How can organisations protect against Shinyhunters attacks?

To defend against Shinyhunters and similar threat actors, organisations should: maintain regular offline backups tested for restoration; implement network segmentation to limit lateral movement; deploy multi-factor authentication on all remote access; use endpoint detection and response (EDR) tools; conduct regular phishing and security awareness training; and monitor threat intelligence feeds for indicators of compromise (IOCs) associated with active groups.