Substack 2025 Data Breach
Media & News / News
Substack 2025 Data Breach
A publishing platform.
The Breach Risk Index (BRI) is a proprietary 0–100 score rating how dangerous a breach is right now, based on how recently the data has been circulating on the dark web and how valuable it is to attackers.
Breach Summary
In October 2025, the publishing platform Substack suffered a data breach that was subsequently circulated more widely in February 2026. The breach exposed 663k account holder records containing email addresses along with publicly visible profile information from Substack accounts, such as publication names and bios. A subset of records also included phone numbers.
Full threat analysis, exploitation vectors, and principal guidance below.
10 additional sections · verified field analysis · defensive doctrine
663K records analyzed
About Substack
Substack is a publishing platform.
Why They Hold Your Data
Substack is a publishing platform. Services like this typically hold email addresses, names, phone numbers, usernames through account registration and normal operations.
Recent Developments
The Substack dataset circulated publicly; treat as part of the standing exposure landscape.
Data Points Exposed
Breach Impact
The exposure created downstream fraud and phishing risk for those affected and drew scrutiny of Substack's data protection.
Exploitation & Downstream Threats
• SIM swap attacks where phone numbers are present | • Targeted phishing campaigns using exposed email addresses
What this means for a principal
A consumer-service breach: contact and account data supports phishing, account takeover and profile enrichment. For a high-profile principal the main risk is credible impersonation and enrichment of existing exposure.
What You Should Do
- Guard against SIM-swap and vishing: add a carrier port-out PIN and verify any 'support' calls independently.
- Do not use unofficial 'am I affected' lookups; several are themselves harvesting operations.
How ObscureIQ Can Help
- Corpus confirmation: determine whether and where the principal (plus household and staff) appear in this dataset and which specific fields are exposed for them.
- Exposure mapping and footprint neutralization: cross-reference against broker-available data and suppress still-removable elements, prioritizing address and phone, since this record re-seeds broker networks.
- ThreatWatch tuned to this incident's identifiers and misuse pattern (impersonation and targeting patterns, not generic credential monitoring).
Protect Yourself
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