Mittwald CM Service, a German hosting provider for web agencies, said in a blog post by founder and managing director Robert Meyer dated 7 November 2026 that an attacker exploited a vulnerability in its Model Context Protocol (MCP) server, which lets customers connect AI assistants to its mStudio platform.

According to the company's timeline, the attacker first tested the MCP-server flaw on the evening of 21 October, moved around the platform as a regular user from 23 October (test accounts, extensions, simple injection attempts), and on 27 October registered another account and exploited the flaw.

Mittwald says its logs show the attacker moved through its systems extremely quickly, which it says indicates the use of AI tools, and that it treats all data from 27 October as compromised.

The company says it detected unusual behaviour on the morning of 4 November, blocked the first attacker account, took parts of its systems offline and shut down the MCP server, which it identified as the entry point.

Mittwald says it forensically examined 56 compromised projects and the MCP server, found no further compromised projects after repeated scans, and currently cannot detect attacker activity; external forensic experts are supporting the analysis and the relevant authorities were informed. mStudio and SSH access were re-enabled on 7 November, websites the company blocked as a precaution remain blocked for now, and the company says its Kundencenter and the websites managed there were not affected.

Mittwald says it will publish a detailed account next week. The Record (Recorded Future News, 9 Nov 2026) notes that Mittwald provided no other evidence of AI involvement and that it is unclear whether the flaw was in Mittwald's own code or in open-source MCP libraries.