--- title: Substack Discloses Security Breach Affecting User... description: Substack disclosed a data breach from October 2025 that went undetected for five months, exposing email addresses, phone numbers, and account metadata of... canonical: https://daily.dev/posts/substack-discloses-security-breach-affecting-user-contact-information-myrjioxys twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Substack Discloses Security Breach Affecting User Contact Information | daily.dev og:description: Substack disclosed a data breach from October 2025 that went undetected for five months, exposing email addresses, phone numbers, and account metadata of... og:url: https://daily.dev/posts/substack-discloses-security-breach-affecting-user-contact-information-myrjioxys og:image: https://api.daily.dev/og/posts/myrJIoXYs.png og:image:alt: Substack Discloses Security Breach Affecting User Contact Information 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 Discloses Security Breach Affecting User Contact Information **[Collections](https://daily.dev/sources/collections)** · 2 min read · 0 upvotes · 0 comments ## Summary Substack disclosed a data breach from October 2025 that went undetected for five months, exposing email addresses, phone numbers, and account metadata of users. Nearly 700,000 user records appeared on cybercrime forums, though passwords and financial data remained secure. The breach resulted from a now-patched vulnerability, and the company is investigating while warning users about potential phishing attempts. The platform's passwordless authentication system using magic links provided some protection during the incident. ## Content Substack has announced a data breach that compromised the email addresses, phone numbers, and account metadata of its users. The breach occurred in October 2025 and remained undetected until February 2026, when the incident was finally uncovered. While sensitive information such as passwords and financial data was not affected, it is reported that nearly 700,000 user records have been posted on cybercrime forums. The unauthorized access was made possible due to a vulnerability which Substack has since patched. The popular newsletter platform is actively conducting an investigation to understand the full scope of the breach and ensure the security of its systems. The breach's specific impact, including the number of its over 50 million active subscriptions affected, has not been made public. There is also no information yet as to why it took five months to detect the intrusion. Substack has warned its users to remain vigilant for phishing attempts, given the exposure of their contact details. The company notes that its use of passwordless authentication through magic links sent to email addresses offers some mitigation against security risks, as no passwords were involved in the breach. This incident underscores the importance of ongoing security vigilance and timely detection of vulnerabilities to protect user data. ## 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 - [Betterment breach scope pegged at 1.4M users](https://daily.dev/posts/betterment-breach-scope-pegged-at-1-4m-users-y8majqbox) · The Register · 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), [#cyber](https://daily.dev/tags/cyber), [#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-discloses-security-breach-affecting-user-contact-information-myrjioxys) ```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 Discloses Security Breach Affecting User Contact Information","url":"https://daily.dev/posts/substack-discloses-security-breach-affecting-user-contact-information-myrjioxys","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/substack-discloses-security-breach-affecting-user-contact-information-myrjioxys"},"datePublished":"2026-02-05T19:58:17.827Z","dateModified":"2026-02-05T21:15:20.007Z","description":"Substack disclosed a data breach from October 2025 that went undetected for five months, exposing email addresses, phone numbers, and account metadata of...","image":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/b4b72df7cfa8f7f5b05c67ff9644477f?_a=AQAEulh","thumbnailUrl":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/b4b72df7cfa8f7f5b05c67ff9644477f?_a=AQAEulh","isAccessibleForFree":true,"articleSection":"Collections","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"Collections","logo":"https://media.daily.dev/image/upload/s--fk_6ycEi--/f_auto,q_auto/v1780996001/logos/collections?_a=BAMAMiWQ0","url":"https://daily.dev/sources/collections"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/substack-discloses-security-breach-affecting-user-contact-information-myrjioxys","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"tech-news,security,cyber,privacy,data-breach","timeRequired":"PT2M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"Collections","item":"https://daily.dev/sources/collections"},{"@type":"ListItem","position":3,"name":"Substack Discloses Security Breach Affecting User Contact Information"}]} ```