The gist: Attackers instrumentalize LLM agents following initial compromise via Marimo vulnerability for lateral movement and credential harvesting.
An unknown threat actor has exploited a vulnerability in Marimo (CVE-2026-39987) to gain access to an internet-accessible notebook and subsequently deployed an AI agent for post-compromise activities.
An unknown threat actor has exploited a recently disclosed vulnerability in Marimo to compromise an internet-accessible Marimo notebook instance. Following initial compromise via CVE-2026-39987, the attacker extracted two cloud credentials from the compromised environment.
The use of an LLM agent for post-compromise operations marks a new level in the instrumentalization of AI systems for cyberattacks. This demonstrates that attackers are using AI-based tools not only for reconnaissance, but deliberately to automate lateral movements and credential harvesting. For CISOs, this represents an additional threat scenario beyond classic post-exploit activities and implies higher automation speed.
This scenario underscores the criticality of promptly patching internet-exposed development and notebook environments and maintaining strong network segmentation as well as credential monitoring. The combination of a known vulnerability and AI-enabled automation significantly increases attackers’ risk of scaling lateral movement.
Source: thehackernews.com · Published May 29, 2026
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