Opportune LLP: Opportune Data Breach Exposes Social Security Numbers

Opportune LLP Suffers Ransomware Attack, Exposing Sensitive Data of Energy Industry Clients

Houston-based global advisory firm Opportune LLP, specializing in the energy sector, disclosed a data breach on September 18, 2026, after the Chaos ransomware group claimed responsibility for the attack. The breach, reported to the Vermont Attorney General, impacted 56 Vermont residents, though the full scope of affected individuals remains unclear.

On July 8, 2026, Chaos posted a claim on the dark web via Tor, asserting they had exfiltrated 750 gigabytes of data from Opportune’s systems. The compromised information included Social Security numbers, though the exact timeline of the intrusion including when the attackers first gained access or when Opportune detected the breach has not been publicly disclosed.

Opportune has begun notifying affected individuals via mailed letters, outlining the incident, the exposed data, and available resources. The firm has not provided further details on the attack’s origin or its response measures. The breach underscores ongoing cybersecurity risks in the energy sector, particularly from ransomware groups targeting sensitive corporate and personal data.

Source: https://www.claimdepot.com/data-breach/opportune-2026

Opportune cybersecurity rating report: https://www.rankiteo.com/company/opportune-llp

"id": "OPP1790303304",
"linkid": "opportune-llp",
"type": "Ransomware",
"date": "7/2026",
"severity": "100",
"impact": "5",
"explanation": "Attack threatening the organization's existence"

{'affected_entities': [{'customers_affected': '56 Vermont residents (full '
                                              'scope unclear)',
                        'industry': 'Energy',
                        'location': 'Houston, Texas, USA',
                        'name': 'Opportune LLP',
                        'type': 'Advisory Firm'}],
 'customer_advisories': 'Mailed letters to affected individuals',
 'data_breach': {'data_exfiltration': '750 gigabytes of data',
                 'personally_identifiable_information': 'Yes',
                 'sensitivity_of_data': 'High',
                 'type_of_data_compromised': ['Social Security numbers',
                                              'Sensitive corporate and '
                                              'personal data']},
 'date_publicly_disclosed': '2026-09-18',
 'description': 'Houston-based global advisory firm Opportune LLP, '
                'specializing in the energy sector, disclosed a data breach on '
                'September 18, 2026, after the Chaos ransomware group claimed '
                'responsibility for the attack. The breach impacted 56 Vermont '
                'residents, though the full scope of affected individuals '
                'remains unclear. The compromised information included Social '
                'Security numbers and other sensitive data.',
 'impact': {'data_compromised': '750 gigabytes of data',
            'identity_theft_risk': 'High (Social Security numbers exposed)'},
 'ransomware': {'data_exfiltration': 'Yes', 'ransomware_strain': 'Chaos'},
 'references': [{'source': 'Dark web (Tor)'},
                {'source': 'Vermont Attorney General'}],
 'regulatory_compliance': {'regulatory_notifications': ['Reported to Vermont '
                                                        'Attorney General']},
 'response': {'communication_strategy': 'Mailed letters to affected '
                                        'individuals'},
 'threat_actor': 'Chaos ransomware group',
 'title': 'Opportune LLP Suffers Ransomware Attack, Exposing Sensitive Data of '
          'Energy Industry Clients',
 'type': 'Ransomware'}