Microsoft disclosed four actively exploited zero-day vulnerabilities being used to attack on-premises versions of Microsoft Exchange Server. The vulnerabilities identified are CVE-2021-26855, CVE-2021-26857, CVE-2021-26858, and CVE-2021-27065, all of which affect Microsoft Exchange Server. Exchange Online is not affected. In the attacks observed, the threat actor used these vulnerabilities to access on-premises Exchange servers which enabled access to email accounts, and allowed installation of additional malware to facilitate long-term access to victim environments. Microsoft Threat Intelligence Center (MSTIC) attributes this campaign with high confidence to HAFNIUM, a group assessed to be state-sponsored and operating out of China, based on observed victimology, tactics and procedures.

The Hash Form – Drag & Drop Form Builder plugin for WordPress is vulnerable to arbitrary file uploads due to missing file type validation in the 'file_upload_action' function in all versions up to, and including, 1.1.0. This makes it possible for unauthenticated attackers to upload arbitrary files on the affected site's server which may make remote code execution possible.