MemberSource Credit Union Files Montana Data Breach Report

MemberSource Credit Union reported a data security incident to Montana regulators in May 2026, stemming from a breach that occurred in June 2025. The incident potentially exposed sensitive personal and financial information for an unspecified number of individuals, prompting vigilance from those affected.

State: Montana
Breach date: June 3, 2025
Reported: May 5, 2026

What may have been exposed

Full Name
Social Security Number
Financial Account Number
Date of Birth
Routing Number
Credit Score Information
Transaction History
Mailing Address

MemberSource Credit Union, a financial cooperative, filed a data breach notification with Montana authorities on May 5, 2026. This filing reported a cybersecurity incident that began on or about June 3, 2025, impacting the credit union's digital network infrastructure.

The reported exposure included a range of sensitive data categories. These were specifically identified as Full Name, Social Security Number, Financial Account Number, Date of Birth, Routing Number, Credit Score Information, Transaction History, and Mailing Address.

Such information, when compromised, carries various risks for affected individuals. The exposure of Full Name, Date of Birth, and Social Security Number can be used in identity theft schemes. Financial Account Number, Routing Number, and Transaction History could potentially facilitate financial fraud, including unauthorized transactions or account access.

For those who receive an official notification from MemberSource Credit Union, it is advisable to review personal financial accounts and credit reports for any suspicious activity. Placing a fraud alert or credit freeze on your credit files with major credit bureaus can help prevent new accounts from being opened in your name. Remain cautious of unsolicited communications that might attempt to exploit this incident.

What to do if you were affected

Based on the categories of information reported in this filing, these steps can help limit the risk of identity theft and fraud.

Freeze your credit
Place a free credit freeze with Equifax, Experian, and TransUnion. A freeze blocks new accounts from being opened in your name and can be lifted anytime.
Watch your financial accounts
Review bank and card statements for unfamiliar activity and turn on transaction alerts. Report anything you don't recognize to your bank right away.
Stay alert to targeted scams
Be cautious of calls, texts, or emails that reference this breach. Legitimate organizations won't ask you to confirm sensitive details through an unsolicited message.
Keep your notification letter
Save the notice you received. It documents that your information was involved and is often needed to enroll in any credit monitoring offered or to join a related legal claim.

Source: Montana Attorney General filing

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