HackingFinancial ServicesFinanceStolen CredentialsCustomer Data InvolvedPIIIdentity (basic)LowContained

CO-OP Credit Union

bd_b6608c610ec41966 · schema v1 · pii pii-v1

Severity

Low

Discovered

Apr 18, 2025

Filed

Oct 20, 2025

To disclose

26 weeks

Affected

18state residents only

Linked

3 filings

Confidence

64%

Full breach record for CO-OP Credit Union →2 incidents on file

Co-op Credit Union notified Montana residents that an unauthorized party accessed an employee email account between April 8 and April 18, 2025. The incident involved the name and other personal data of affected individuals. The credit union engaged forensic investigators and is offering one year of complimentary credit monitoring via Experian IdentityWorks.

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Incident timeline

undetected · 10 days

discovery → filing · 26 weeks / 185 days

Apr 8, 2025

Begins

Apr 18, 2025

Discovered

Oct 20, 2025

Filed

vs. sector median

+18 wks slower

This filing is one of 3 about the same incident.View merged incident

Linked disclosures

Why this link?

Regulatory filings (2) · sorted by filing gap

Nebraska State AGbd_47ab496b78cc9ea12025-10-20Verified
Massachusetts State AGbd_67218060f7e99fa42025-10-21 · +1dVerified

Name: CO-OP Credit Union
norm: co op credit union

Name: CO-OP Credit Union
norm: co op credit union
Industry: Financial Servicesllm

Discovered: Apr 18, 2025
Breach occurred: Apr 8, 2025 – Apr 18, 2025
Undetected for: 10 daysoccurrence → discovery
Materiality determined: —
Notification sent: —
Affected individuals: 18state-resident count only
Data types: PIIIdentity (basic)
Attack vector: Unauthorized Access
MITRE ATT&CK: T1078 Valid Accounts
Threat actor: External
Initial access: valid_credentials

During the incident: Launched an investigation
Engaged a third-party forensic firm to further investigate and confirm the security of our email environment
Arranged for you to enroll in a complimentary, one-year membership of Experian IdentityWorksSM Credit 3B
Changes made: Confirm the security of our email environment
Source: Quoted from the filing itself, not independently verified.

Time to disclose: 26 weeks(185 days from discovery to filing)
Compliance flags: — (clock not assessable for this source)

Status: No extraction artifact recorded for this disclosure.

Filing propagation · 3 filings · 3 states

View merged incident ↗

Nebraska State AGOct 20 · first

Montana State AGOct 20 · first · this page

Massachusetts State AG+1d

Evidence ladder

Leak-site claim

Attacker assertion only. Establishes: claim date, group, alleged victim.

Press / market report

Unlocks: incident narrative, operational impact. Still no compliance clock.

State AG / regulator filingThis record

Unlocks: discovery date, data types, affected count, compliance clock.

SEC 8-K / victim statement

Unlocks: materiality, stated response, full audit trail. Ceiling removed.

Source URL: https://dojmt.gov/wp-content/uploads/2025/10/Consumer-notification-letter-27.pdf
DisclosureLens links to the originating regulator URL — full filing bodies are not redistributed from public surfaces (§4.5).
Filed at: Oct 20, 2025
Raw hash: 6e7f52d22647e3eeb73edfa414d89c03ffc0842c09a02eee117bc36dd7c18333

Linked disclosures

Regulatory filings (2) · sorted by filing gap

Reporting entityCO-OP Credit Union

Victim entityCO-OP Credit Union

Incidentdiscovered Apr 18, 2025

Stated responseLaunched an investigation

Complianceclock not assessable

Extraction provenanceno artifact recorded

Source provenancedojmt.gov