RCE on GMO Flatt Security Research

Poisoning Claude Code: One GitHub Issue to Break the Supply Chain

Mon, 01 Jun 2026 00:00:00 +0000

Introduction

Hello, I’m RyotaK ( @ryotkak ), a security researcher at GMO Flatt Security Inc.

After publishing my previous article ( Pwning Claude Code in 8 Different Ways ), I continued investigating Claude-related products and found several more vulnerabilities.

In this article, I will explain a vulnerability in Claude Code’s GitHub Actions that could allow an attacker to compromise any repository that uses the Claude Code workflow, including Anthropic’s own repositories.¹

Note: Variants of the misconfiguration issues described in this article were actively exploited in the wild before this article was published.

Remote Command Execution in Google Cloud with Single Directory Deletion

Mon, 23 Mar 2026 00:00:00 +0000

Introduction

Hello, I’m RyotaK (@ryotkak ), a security engineer at GMO Flatt Security Inc.

A while ago, I participated in the Google Cloud VRP bugSWAT, a live hacking event organized by Google.

During this event, I discovered a remote command execution vulnerability in one of Google Cloud’s services. As the vulnerability has now been fixed, I would like to share the technical details in this article.

TL;DR

Google Cloud has a product called Looker, and this product has a feature to manage Git repositories.

Pwning Claude Code in 8 Different Ways

Mon, 12 Jan 2026 00:00:00 +0000

Introduction

Hello, I’m RyotaK (@ryotkak ), a security engineer at GMO Flatt Security Inc.

A few months ago, I came across an interesting behavior while using Claude Code—it executed a command without my approval.

Since I wasn’t using the permission bypass mode, I decided to investigate further to understand why it was able to execute commands without explicit approval.

TL;DR

I discovered 8 ways to execute arbitrary commands in Claude Code without user approval.

CVE-2025-59489: Arbitrary Code Execution in Unity Runtime

Fri, 03 Oct 2025 00:00:00 +0000

Introduction

Hello, I’m RyotaK (@ryotkak ), a security engineer at GMO Flatt Security Inc.

In May 2025, I participated in the Meta Bug Bounty Researcher Conference 2025. During this event, I discovered a vulnerability (CVE-2025-59489) in the Unity Runtime that affects games and applications built on Unity 2017.1 and later.

In this article, I will explain the technical aspects of this vulnerability and its impact.

This vulnerability was disclosed to Unity following responsible disclosure practices.
Unity has since released patches for Unity 2019.1 and later, as well as a Unity Binary Patch tool to address the issue, and I strongly encourage developers to download the updated versions of Unity, recompile affected games or applications, and republish as soon as possible.

Achieving RCE in famous Japanese chat tool with an obsolete Electron feature

Wed, 19 Feb 2025 00:00:00 +0000

Introduction

Hello, I’m RyotaK (@ryotkak ), a security engineer at GMO Flatt Security Inc.

A while ago, I reported a remote code execution vulnerability that chains multiple problems in Chatwork, a popular communication tool in Japan.

In the report that I sent to the bug bounty platform, I used an obsolete feature of Electron to escalate to the preload context.
As the vulnerability was interesting, I’m writing this article to share the details of it.