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New Windows RDP phishing warning: Caution: Unknown remote connection

Feeds.4Sysops •IT Experts • April 21, 2026

The April 2026 Patch Tuesday updates add anti-phishing protection to the Windows Remote Desktop client (mstsc.exe). The change — assigned CVE-2026-26151 — means that opening an .rdp file now triggers a security dialog that lists all requested resource-sharing settings, each disabled by default. Files without a verifiable publisher show a red "Caution: Unknown remote connection" banner. The update affects Windows 10 and Windows 11 versions 23H2 and later. Source

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New RDP Phishing Warning Implemented in April 2026 Windows Update Microsoft released a significant update to the Windows Remote Desktop client (mstsc.exe) on April 14, 2026, addressing vulnerabilities associated with Remote Desktop Protocol (.rdp) files. The update introduces a security dialog that alerts users to potential phishing attempts by displaying a 'Caution: Unknown remote connection' banner for files lacking a verifiable publisher. This change is part of the April 2026 Patch Tuesday updates and is applicable to Windows 10 and Windows 11 versions 23H2 and later. The update is designated as CVE-2026-26151. The new feature aims to mitigate the rising threat of phishing attacks exploiting .rdp files, which have been increasingly weaponized by cybercriminals. Users are encouraged to be vigilant when opening .rdp files, especially from untrusted sources. The update enhances user awareness and security against potential remote access exploits. 10 sources 58

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New Windows RDP phishing warning: Caution: Unknown remote connection

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Extracted Entities

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