ToolShell SharePoint Zero-Days Exploited in the Wild
🔒 Microsoft and ESET reported active exploitation of a SharePoint Server vulnerability cluster called ToolShell, comprising CVE-2025-53770 (remote code execution) and CVE-2025-53771 (server spoofing). Attacks began on July 17, 2025, and target on-prem SharePoint Subscription Edition, SharePoint 2019 and SharePoint 2016; SharePoint Online is not affected. Operators deployed webshells — notably spinstall0.aspx (detected as MSIL/Webshell.JS) and several ghostfile*.aspx samples — to bypass MFA/SSO, exfiltrate data and move laterally across integrated Microsoft services. Microsoft and ESET confirmed patches were released on July 22, and ESET published IoCs and telemetry to assist defenders.