{"id":750658,"date":"2026-10-31T14:35:24","date_gmt":"2026-10-31T11:35:24","guid":{"rendered":"https:\/\/buradabiliyorum.com\/en\/anthropic-denies-breach-as-tampered-claude-code-extension-hits-cursor-users\/"},"modified":"2026-10-31T14:35:24","modified_gmt":"2026-10-31T11:35:24","slug":"anthropic-denies-breach-as-tampered-claude-code-extension-hits-cursor-users","status":"publish","type":"post","link":"https:\/\/buradabiliyorum.com\/en\/anthropic-denies-breach-as-tampered-claude-code-extension-hits-cursor-users\/","title":{"rendered":"Anthropic denies breach as tampered Claude Code extension hits Cursor users"},"content":{"rendered":"<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_89 counter-hierarchy ez-toc-counter ez-toc-custom ez-toc-container-direction\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Table of Contents<\/p>\n<label for=\"ez-toc-cssicon-toggle-item-6aec558d17570\" class=\"ez-toc-cssicon-toggle-label\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #dd3333;color:#dd3333\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #dd3333;color:#dd3333\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/label><input type=\"checkbox\"  id=\"ez-toc-cssicon-toggle-item-6aec558d17570\" checked aria-label=\"Toggle\" \/><nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/buradabiliyorum.com\/en\/anthropic-denies-breach-as-tampered-claude-code-extension-hits-cursor-users\/#What_Cursor_found\" >What Cursor found<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/buradabiliyorum.com\/en\/anthropic-denies-breach-as-tampered-claude-code-extension-hits-cursor-users\/#Anthropic_%E2%80%98didnt_build_or_publish\" >Anthropic: \u2018didn\u2019t build or publish\u2019<\/a><\/li><\/ul><\/nav><\/div>\n<p><img decoding=\"async\" src=\"https:\/\/media.thenextweb.com\/2026\/10\/source-code-terminal-dark-monitor-close-up.avif\" \/><\/p>\n<div id=\"article-main-content\">\n<p>A tampered copy of Anthropic\u2019s Claude Code extension sat in Cursor\u2019s extension marketplace for about 11 hours on Thursday 29 October. It reached up to 5,000 users. The malicious versions tried to plant an SSH backdoor on developers\u2019 machines, Cursor said in a <a rel=\"nofollow\" target=\"_blank\" href=\"https:\/\/cursor.com\/blog\/claude-code-extension-security-notice\" target=\"_blank\" rel=\"nofollow noopener\">security notice<\/a>.<\/p>\n<p>Anthropic says nobody breached its own systems. A security firm that studied the attack says the extension went out through Anthropic\u2019s official account on Cursor. Neither Anthropic nor Cursor has said how the attacker got access.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"What_Cursor_found\"><\/span>What Cursor found<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>The affected versions were 2.1.312 and 2.1.313 for Windows and macOS. They were live from about 2:27am to 1:35pm Pacific time. Cursor, which SpaceX acquired earlier this year, said Anthropic did not develop the code.<\/p>\n<p>The extension collected details about each machine and its user, including the hostname, username, Git email and public IP address. It then tried to add the attacker\u2019s SSH key and turn on the computer\u2019s SSH service. It also tried to open a reverse tunnel to the attacker\u2019s server.<\/p>\n<p>That last step needs administrator rights, which the extension lacks on most macOS and Windows machines. So it would usually fail, Cursor said. But the key, the persistence <a href=\"https:\/\/buradabiliyorum.com\/en\/category\/download-scripts-themes-apps\/\" data-internallinksmanager029f6b8e52c=\"9\" title=\"Download Scripts &amp; Themes &amp; Apps\" target=\"_blank\" rel=\"noopener\">script<\/a>s and the data upload still went through. Uninstalling the extension may not be enough to remove them.<\/p>\n<blockquote class=\"twitter-tweet\">\n<p dir=\"ltr\" lang=\"en\">We identified a security incident affecting a modified Claude Code VS Code extension accessed through our Cursor IDE extension marketplace, impacting at most 5,000 users. This malicious version of the extension was not developed by Anthropic. It does not impact other extensions downloaded from the http:\/\/cursor.com\/marketplace, Grok Bot, Grok or our other SpaceXSI products.<\/p>\n<p>In response, we took down our extension marketplace this afternoon, worked with relevant providers to neutralize the malware, and have reinstated the marketplace after confirming there is no further risk.<\/p>\n<p>If affected, please review instructions in this blog post to understand how to find the malicious package and establish a path to mitigate any potential impact. We are asking all customers update to Claude Code for VS Code version 2.1.314: https:\/\/cursor.com\/blog\/claude-code-extension-security-notice<\/p>\n<p>Cursor (@cursor_ai) <a rel=\"nofollow\" target=\"_blank\" href=\"https:\/\/x.com\/cursor_ai\/status\/2116074289053175808\" target=\"_blank\" rel=\"nofollow noopener\">October 30, 2026<\/a><\/p>\n<\/blockquote>\n<p>Cursor removed the versions and shut its whole marketplace while it checked the other extensions. It then rotated its keys and reopened it. It also had the attacker\u2019s server taken offline. It has published scripts to check for and remove the backdoor.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Anthropic_%E2%80%98didnt_build_or_publish\"><\/span>Anthropic: \u2018didn\u2019t build or publish\u2019<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Felix Rieseberg, a member of Anthropic\u2019s technical staff, responded in a post on X.<\/p>\n<blockquote class=\"twitter-tweet\">\n<p dir=\"ltr\" lang=\"en\">We\u2019re working with Cursor on this incident, but it wasn\u2019t a compromise of Anthropic\u2019s systems or employee laptops. A malicious actor used access to Cursor\u2019s marketplace to publish a tampered copy of the Claude Code extension, which we didn\u2019t build or publish. The versions on our official channels are not affected and this only impacts Cursor users.<\/p>\n<p>Felix Rieseberg (@felixrieseberg) <a rel=\"nofollow\" target=\"_blank\" href=\"https:\/\/x.com\/felixrieseberg\/status\/2116170451466543578\" target=\"_blank\" rel=\"nofollow noopener\">October 30, 2026<\/a><\/p>\n<\/blockquote>\n<p>The security firm Phorion first flagged the <a rel=\"nofollow\" target=\"_blank\" href=\"https:\/\/phorion.io\/blog\/offical-claude-code-vsx-compromise\/\" target=\"_blank\" rel=\"nofollow noopener\">compromise<\/a>. Its co-founder and chief <a href=\"https:\/\/buradabiliyorum.com\/en\/category\/technology\/\" data-internallinksmanager029f6b8e52c=\"4\" title=\"Technology\" target=\"_blank\" rel=\"noopener\">technology<\/a> officer, Luke Roberts, told <a rel=\"nofollow\" target=\"_blank\" href=\"https:\/\/arstechnica.com\/security\/2026\/10\/anthropic-vs-code-extension-on-cursor-backdoored-for-nearly-12-hours\/\" target=\"_blank\" rel=\"nofollow noopener\">Ars Technica<\/a> that the attacker reached the official distribution channel.<\/p>\n<blockquote>\n<p>\u201cThe malicious version 2.1.313 was posted to the official Anthropic account, effectively superseding 2.1.312,\u201d Roberts told Ars.<\/p>\n<\/blockquote>\n<p>Independent researcher Kevin Beaumont made the same point, Dan Goodin reported for Ars. Extensions update automatically in Cursor by default, Roberts said. Cursor has told users to move to a clean version, 2.1.314.<\/p>\n<p>The malware also sent the names of up to 40 environment variables matching keys, tokens and secrets, but not their values, Phorion found. That gives the attacker a quick list of which cloud credentials sit on each machine.<\/p>\n<p>Supply-chain attacks on developer tools have hit npm packages this year, and researchers have warned that AI coding tools could amplify such attacks.<\/p>\n<\/p><\/div>\n<blockquote><p><strong><span style=\"color: #ff6600;\">If you liked the article, do not forget to share it with your friends. Follow us on\u00a0<span style=\"color: #ff0000;\"><a style=\"color: #ff0000;\" href=\"https:\/\/news.google.com\/publications\/CAAqBwgKMN63nwsw68G3Aw\" target=\"_blank\" rel=\"nofollow noopener noreferrer\">Google News<\/a><\/span>\u00a0too, click on the star and choose us from your favorites.<\/span><\/strong><\/p><\/blockquote>\n<blockquote>\n<p style=\"text-align: center;\"><strong>If you want to read more like this article, you can visit our <span style=\"color: #ff9900;\"><a style=\"color: #ff9900;\" href=\"https:\/\/buradabiliyorum.com\/en\/category\/technology\/\" target=\"_blank\" >Technology category.<\/a><\/span><\/strong><\/p>\n<\/blockquote>\n<p><span style=\"color: black;\"><a style=\"color: #ff9900;\" href=\"https:\/\/thenextweb.com\/news\/tampered-claude-code-extension-cursor-ssh-backdoor\" target=\"_blank\" >Source<\/a><\/span><\/p>\n","protected":false},"excerpt":{"rendered":"<p>A tampered copy of Anthropic\u2019s Claude Code extension sat in Cursor\u2019s extension marketplace for about 11 hours on Thursday 29 October. It reached up to 5,000 users. The malicious versions tried to plant an SSH backdoor on developers\u2019 machines, Cursor said in a security notice. Anthropic says nobody breached its own systems. A security firm&#8230;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"fifu_image_url":"","fifu_image_alt":"","footnotes":""},"categories":[18],"tags":[],"class_list":["post-750658","post","type-post","status-publish","format-standard","hentry","category-technology"],"_links":{"self":[{"href":"https:\/\/buradabiliyorum.com\/en\/wp-json\/wp\/v2\/posts\/750658","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/buradabiliyorum.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/buradabiliyorum.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/buradabiliyorum.com\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/buradabiliyorum.com\/en\/wp-json\/wp\/v2\/comments?post=750658"}],"version-history":[{"count":0,"href":"https:\/\/buradabiliyorum.com\/en\/wp-json\/wp\/v2\/posts\/750658\/revisions"}],"wp:attachment":[{"href":"https:\/\/buradabiliyorum.com\/en\/wp-json\/wp\/v2\/media?parent=750658"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/buradabiliyorum.com\/en\/wp-json\/wp\/v2\/categories?post=750658"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/buradabiliyorum.com\/en\/wp-json\/wp\/v2\/tags?post=750658"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}