{"id":234131,"date":"2026-03-27T03:16:02","date_gmt":"2026-03-27T08:16:02","guid":{"rendered":"https:\/\/lifeboat.com\/blog\/2026\/03\/claude-extension-flaw-enabled-zero-click-xss-prompt-injection-via-any-website"},"modified":"2026-03-27T03:16:02","modified_gmt":"2026-03-27T08:16:02","slug":"claude-extension-flaw-enabled-zero-click-xss-prompt-injection-via-any-website","status":"publish","type":"post","link":"https:\/\/lifeboat.com\/blog\/2026\/03\/claude-extension-flaw-enabled-zero-click-xss-prompt-injection-via-any-website","title":{"rendered":"Claude Extension Flaw Enabled Zero-Click XSS Prompt Injection via Any Website"},"content":{"rendered":"<p><\/p>\n<p><iframe style=\"display: block; margin: 0 auto; width: 100%; aspect-ratio: 4\/3; object-fit: contain;\" src=\"https:\/\/www.youtube.com\/embed\/5EPnC9SzhOw?feature=oembed\" frameborder=\"0\" allow=\"accelerometer; autoplay; encrypted-media; gyroscope;\n   picture-in-picture\" allowfullscreen><\/iframe><\/p>\n<p>Specifically, the XSS vulnerability enables the execution of arbitrary JavaScript code in the context of \u201ca-cdn.claude[.]ai.\u201d A threat actor could leverage this behavior to inject JavaScript that issues a prompt to the Claude extension.<\/p>\n<p>The extension, for its part, allows the prompt to land in Claude\u2019s sidebar as if it\u2019s a legitimate user request simply because it comes from an allow-listed domain.<\/p>\n<p>\u201cThe attacker\u2019s page embeds the vulnerable Arkose component in a hidden, sends the XSS payload via postMessage, and the injected script fires the prompt to the extension,\u201d Yomtov explained. \u201cThe victim sees nothing.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Specifically, the XSS vulnerability enables the execution of arbitrary JavaScript code in the context of \u201ca-cdn.claude[.]ai.\u201d A threat actor could leverage this behavior to inject JavaScript that issues a prompt to the Claude extension. The extension, for its part, allows the prompt to land in Claude\u2019s sidebar as if it\u2019s a legitimate user request simply [\u2026]<\/p>\n","protected":false},"author":427,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[6],"tags":[],"class_list":["post-234131","post","type-post","status-publish","format-standard","hentry","category-robotics-ai"],"_links":{"self":[{"href":"https:\/\/lifeboat.com\/blog\/wp-json\/wp\/v2\/posts\/234131","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/lifeboat.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/lifeboat.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/lifeboat.com\/blog\/wp-json\/wp\/v2\/users\/427"}],"replies":[{"embeddable":true,"href":"https:\/\/lifeboat.com\/blog\/wp-json\/wp\/v2\/comments?post=234131"}],"version-history":[{"count":0,"href":"https:\/\/lifeboat.com\/blog\/wp-json\/wp\/v2\/posts\/234131\/revisions"}],"wp:attachment":[{"href":"https:\/\/lifeboat.com\/blog\/wp-json\/wp\/v2\/media?parent=234131"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/lifeboat.com\/blog\/wp-json\/wp\/v2\/categories?post=234131"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/lifeboat.com\/blog\/wp-json\/wp\/v2\/tags?post=234131"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}