Threat watch / Attack
Mittwald: an attacker used a flaw in the web host's AI assistant server to compromise 56 customer projects
German web host Mittwald says an attacker exploited a weakness in the MCP server of its mStudio platform, the interface that lets customers connect AI assistants to their hosting. The attacker went unnoticed from October 27 to November 4 and compromised 56 customer projects. Mittwald's CEO says the speed of the attack, sometimes seconds between steps, points to the use of AI tools.
- Sector
- Tech & SaaS
- Way in
- Software flaw
- Product or vendor
- Mittwald mStudio
- How it happened
- Mittwald says the attacker first tested a weakness in the MCP server of mStudio on the evening of October 21. From October 23 he behaved like a normal user, registering test accounts and trying simple injections. On October 27 he registered another account and, five minutes later, deliberately exploited the gap in the MCP server. Mittwald has not described the flaw itself, and The Record notes it is unclear whether it sat in Mittwald's own code or in open-source MCP libraries.[1][2] Checked 10 Nov 2026
- What was stolen
- Not public yet Checked 10 Nov 2026
- Who was impacted
- 56 compromised customer projects, as of November 6. Mittwald treats all data from October 27 onward as compromised and keeps the affected websites locked as a precaution. It says the customer centre and the websites managed there were not affected at any time. All mStudio users lost login and SSH access on November 5 until the platform was restored on November 7.[1] Checked 10 Nov 2026
- Threat actor
- Not attributed
Timeline
- In the evening, the attacker first tests a weakness in the mStudio MCP server, according to Mittwald. [1]
- At 14:58 the attacker registers another account and at 15:03 exploits the MCP server flaw. [1]
- Mittwald detects the intrusion in the morning, blocks the first attacker account at 11:11 and switches off the MCP server. [1]
- Mittwald suspends registration, blocks mStudio logins and SSH access to customer projects, and informs the authorities. [1]
- mStudio and SSH access are restored and passkeys can be set up. CEO Robert Meyer publishes an account of the incident, writing that only seconds sometimes passed between steps, which "points to the use of AI tools". He promises a detailed report the following week. [1][2]
- The Record notes that Mittwald gave no other evidence of AI use and did not say whether it could tell AI tools apart from conventional scripts. [2]