--- title: Substack data breach leaks users’ email addresses and... description: Substack discovered a data breach on February 3, 2026, that exposed email addresses, phone numbers, and internal metadata of an unknown number of users. The... canonical: https://daily.dev/posts/substack-data-breach-leaks-users-email-addresses-and-phone-numbers-szgeevzfy twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Substack data breach leaks users’ email addresses and phone numbers | daily.dev og:description: Substack discovered a data breach on February 3, 2026, that exposed email addresses, phone numbers, and internal metadata of an unknown number of users. The... og:url: https://daily.dev/posts/substack-data-breach-leaks-users-email-addresses-and-phone-numbers-szgeevzfy og:image: https://api.daily.dev/og/posts/SzgEeVZFY.png og:image:alt: Substack data breach leaks users’ email addresses and phone numbers og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Substack data breach leaks users’ email addresses and phone numbers **[CSO Online](https://daily.dev/sources/csoonline)** · 4 min read · 0 upvotes · 0 comments ## Summary Substack discovered a data breach on February 3, 2026, that exposed email addresses, phone numbers, and internal metadata of an unknown number of users. The breach occurred in October 2025 but went undetected for four months. Dark web sources claim nearly 700,000 records were compromised, though this remains unconfirmed. The exposed data did not include passwords, credit card numbers, or financial information. Substack uses passwordless authentication via magic links sent to email addresses, which mitigates some security risks. The company has fixed the vulnerability and is conducting a full investigation. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Similar posts on daily.dev - [Have I Been Pwned: SoundCloud Data Breach](https://daily.dev/posts/have-i-been-pwned-soundcloud-data-breach-sddcswlvy) · Hacker News · 0 upvotes · 0 comments - [DoorDash confirms data breach impacting users’ phone numbers and physical addresses](https://daily.dev/posts/doordash-confirms-data-breach-impacting-users-phone-numbers-and-physical-addresses-uqflwqnoi) · TechCrunch · 0 upvotes · 0 comments - [BreachForums Breach Exposes Names of 324K Cybercriminals, Upends the Threat Intel Game](https://daily.dev/posts/breachforums-breach-exposes-names-of-324k-cybercriminals-upends-the-threat-intel-game-gniyjeusk) · Security Boulevard · 0 upvotes · 0 comments --- Tags: [#tech-news](https://daily.dev/tags/tech-news), [#security](https://daily.dev/tags/security), [#authentication](https://daily.dev/tags/authentication), [#privacy](https://daily.dev/tags/privacy), [#data-breach](https://daily.dev/tags/data-breach) [View this post on daily.dev](https://daily.dev/posts/substack-data-breach-leaks-users-email-addresses-and-phone-numbers-szgeevzfy) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Substack data breach leaks users’ email addresses and phone numbers","url":"https://daily.dev/posts/substack-data-breach-leaks-users-email-addresses-and-phone-numbers-szgeevzfy","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/substack-data-breach-leaks-users-email-addresses-and-phone-numbers-szgeevzfy"},"datePublished":"2026-02-05T21:14:37.479Z","dateModified":"2026-02-26T21:09:59.846Z","description":"Substack discovered a data breach on February 3, 2026, that exposed email addresses, phone numbers, and internal metadata of an unknown number of users. 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