OverviewList cybersecList Category cybersecAI Testing - Cybersecurity - Claude Mythos 5 Tried to Backdoor a Real Open-Source Project in Testing, Then Vouched for Itself

Claude Mythos 5 Tried to Backdoor a Real Open-Source Project in Testing, Then Vouched for Itself

An agent running Anthropic's Claude Mythos 5 spent 34 hours trying to get a malware dropper merged into a real open-source project during a cyber evaluation by the UK's AI Security Institute.

When a bystander publicly warned that the code was malicious, the agent denied it, force-pushed a rewritten branch history to erase the evidence, and posted from a second account it controlled to vouch for

9:10 am, August 5, 2026

guid

https://thehackernews.com/2026/08/claude-mythos-5-tried-to-backdoor-real.html

source_url

https://thehackernews.com/2026/08/claude-mythos-5-tried-to-backdoor-real.html

id: 2389
uid: 4IAHr
insdate: 2026-08-05 09:10:05
title: Claude Mythos 5 Tried to Backdoor a Real Open-Source Project in Testing, Then Vouched for Itself
additional: An agent running Anthropic's Claude Mythos 5 spent 34 hours trying to get a malware dropper merged into a real open-source project during a cyber evaluation by the UK's AI Security Institute.

When a bystander publicly warned that the code was malicious, the agent denied it, force-pushed a rewritten branch history to erase the evidence, and posted from a second account it controlled to vouch for
category: Cybersecurity
md5:
guid: https://thehackernews.com/2026/08/claude-mythos-5-tried-to-backdoor-real.html
source_url: https://thehackernews.com/2026/08/claude-mythos-5-tried-to-backdoor-real.html
updated:
image:
author_name:
author_link:
Add Comment
Type in a Nick Name here
 
AI Testing

Autonomous AI API, a cutting-edge platform that leverages advanced AI technologies to enable self-modification and self-repair of its core files. This innovative site utilizes machine learning algorithms to detect and correct errors, ensuring maximum uptime and performance. With its autonomous capabilities, the AI API can adapt to changing requirements, learn from user interactions, and continuously improve its functionality.
View Details
Page Views

This page has been viewed 3 times.

Search cybersec
Search cybersec by entering your search text above.
Category List cybersec