{"description":"Trending threats, MITRE ATT\u0026CK coverage, and detection metadata. Fed continuously.","favicon":"https://feed.craftedsignal.io/favicon-32x32.png","feed_url":"https://feed.craftedsignal.io/tags/m365-copilot/feed.json","home_page_url":"https://feed.craftedsignal.io/","icon":"https://feed.craftedsignal.io/apple-touch-icon.png","items":[{"_cs_actors":[],"_cs_cpes":[],"_cs_cves":[{"cvss":7.5,"id":"CVE-2026-26129"}],"_cs_exploited":false,"_cs_has_poc":false,"_cs_poc_references":[],"_cs_products":["M365 Copilot"],"_cs_severities":["high"],"_cs_tags":["cve","information disclosure","cloud","m365 copilot"],"_cs_type":"advisory","_cs_vendors":["Microsoft"],"content_html":"\u003cp\u003eOn May 7, 2026, CVE-2026-26129 was published, detailing an information disclosure vulnerability within Microsoft's M365 Copilot. The vulnerability stems from improper neutralization of special elements within the application, potentially enabling unauthorized attackers to access sensitive information over a network. Microsoft has assessed the vulnerability as having a CVSS v3.1 score of 7.5 (High), indicating a significant risk. Defenders should prioritize detection and mitigation strategies to prevent potential data breaches.\u003c/p\u003e\n\u003ch2 id=\"attack-chain\"\u003eAttack Chain\u003c/h2\u003e\n\u003col\u003e\n\u003cli\u003eAn attacker identifies an M365 Copilot instance exposed to network traffic.\u003c/li\u003e\n\u003cli\u003eThe attacker crafts a malicious input containing special elements designed to exploit the improper neutralization vulnerability (CVE-2026-26129).\u003c/li\u003e\n\u003cli\u003eThe crafted input is sent to the M365 Copilot instance via a network request.\u003c/li\u003e\n\u003cli\u003eM365 Copilot fails to properly neutralize the special elements within the input.\u003c/li\u003e\n\u003cli\u003eThe special elements are processed, leading to unintended data access.\u003c/li\u003e\n\u003cli\u003eSensitive information is extracted by the attacker.\u003c/li\u003e\n\u003cli\u003eThe extracted information is transmitted over the network to a location controlled by the attacker.\u003c/li\u003e\n\u003cli\u003eThe attacker gains unauthorized access to the disclosed information.\u003c/li\u003e\n\u003c/ol\u003e\n\u003ch2 id=\"impact\"\u003eImpact\u003c/h2\u003e\n\u003cp\u003eSuccessful exploitation of CVE-2026-26129 can lead to the unauthorized disclosure of sensitive information accessible by M365 Copilot. The impact could range from exposure of internal documents and communications to the revelation of proprietary data and confidential customer information. The number of potential victims is dependent on the scope of M365 Copilot deployments and the sensitivity of the data it handles. A successful attack could result in significant reputational damage, financial losses, and legal liabilities for affected organizations.\u003c/p\u003e\n\u003ch2 id=\"recommendation\"\u003eRecommendation\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003eApply the security update provided by Microsoft to address CVE-2026-26129 as soon as possible, referencing the advisory at \u003ca href=\"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-26129\"\u003ehttps://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-26129\u003c/a\u003e.\u003c/li\u003e\n\u003cli\u003eDeploy the Sigma rule \u0026quot;Detect M365 Copilot Special Element Injection Attempt\u0026quot; to identify potential exploitation attempts based on specific special characters in network requests.\u003c/li\u003e\n\u003cli\u003eMonitor network traffic for suspicious patterns indicative of information disclosure, focusing on communications originating from M365 Copilot instances.\u003c/li\u003e\n\u003cli\u003eReview and strengthen input validation and output encoding mechanisms within M365 Copilot to prevent future instances of improper neutralization, referencing CWE-138.\u003c/li\u003e\n\u003c/ul\u003e\n","date_modified":"2026-05-07T22:16:33Z","date_published":"2026-05-07T22:16:33Z","id":"https://feed.craftedsignal.io/briefs/2026-05-07-m365-copilot-info-disclosure/","summary":"CVE-2026-26129 is a high-severity vulnerability in Microsoft's M365 Copilot that allows an unauthorized attacker to disclose information over a network due to improper neutralization of special elements.","title":"M365 Copilot Information Disclosure Vulnerability (CVE-2026-26129)","url":"https://feed.craftedsignal.io/briefs/2026-05-07-m365-copilot-info-disclosure/"}],"language":"en","title":"CraftedSignal Threat Feed - M365 Copilot","version":"https://jsonfeed.org/version/1.1"}