HackingFinancial ServicesFinanceSupply Chain (3P Vendor)Customer Data InvolvedPIIIdentity (basic)Financial accountLowContained

M&T BANK CORPORATION

bd_476c2c623aefc097 · schema v1 · pii pii-v1

Severity

Low

Discovered

Aug 1, 2025

Filed

Apr 17, 2026

To disclose

37 weeks

Affected

462state residents only

Linked

2 filings

Confidence

65%

Full breach record for M&T BANK CORPORATION →13 incidents on file

M&T Bank notified customers in April 2026 that a third-party service provider experienced a security incident in August 2025. M&T's systems were not directly affected. The provider securely removed customer data. M&T is offering 24 months of Equifax credit monitoring and monitoring accounts for fraud.

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Massachusetts clock✗ MA AG >90d37 weeks discovery → filing

Incident timeline

discovery → filing · 37 weeks / 259 days

Aug 1, 2025

Discovered

Apr 17, 2026

Filed

vs. sector median

+28 wks slower

This filing is one of 2 about the same incident.View merged incident

Linked disclosures

Why this link?

Regulatory filings (1) · sorted by filing gap

Nebraska State AGbd_72e6cad186791aba2026-04-17Verified

Name: M&T BANK CORPORATION
norm: m t bank
Domain: mtb.com

Name: M&T BANK CORPORATION
norm: m t bank
Domain: mtb.com
Industry: Financial Servicesllm

Discovered: Aug 1, 2025
Materiality determined: —
Notification sent: Apr 17, 2026
Affected individuals: 462state-resident count only
Data types: PIIIdentity (basic)Financial account
Attack vector: Third-Party / Supply Chain
Threat actor: External

During the incident: Began a comprehensive review
Worked closely with the provider to assess the situation, understand its scope, and determine what data was affected
Confirmed that the service provider has securely removed your data from its systems
Will continue to closely monitor your accounts for potentially fraudulent activity
Offering credit monitoring services from Equifax at no cost for 24 months
Changes made: Confirmed that the service provider has securely removed your data from its systems
Source: Quoted from the filing itself, not independently verified.

Time to disclose: 37 weeks(259 days from discovery to filing)
Compliance flags: MA AG >90d
Discovery-date grounding: letter-groundedThe discovery date is the detection date narrated in the notification letter — the defensible tier.

Status: No extraction artifact recorded for this disclosure.

Filing propagation · 2 filings · 2 states

View merged incident ↗

Nebraska State AGApr 17 · first

Massachusetts State AGApr 17 · first · this page

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://www.mass.gov/doc/2026-597-mt-bank/download
DisclosureLens links to the originating regulator URL — full filing bodies are not redistributed from public surfaces (§4.5).
Filed at: Apr 17, 2026
Raw hash: 72b2fb8b79d9b75769f2722623ea83c4f888cb25f81dc7289ccd537b93bd1007

Linked disclosures

Regulatory filings (1) · sorted by filing gap

Reporting entityM&T BANK CORPORATION

Victim entityM&T BANK CORPORATION

Incidentdiscovered Aug 1, 2025

Stated responseBegan a comprehensive review

ComplianceMA AG >90d

Extraction provenanceno artifact recorded

Source provenancewww.mass.gov