Malicious Next.js Repositories Target Developers

Software supply chain attacks are no longer limited to package managers or CI/CD pipelines. Threat actors are now directly targeting developers through malicious Next.js repositories, disguised as legitimate job assessments and open-source projects.

Microsoft recently warned of a coordinated campaign in which attackers lure developers into cloning and executing poisoned code. Once run, the project silently connects to attacker-controlled command-and-control (C2) infrastructure, granting remote access and exposing sensitive development assets.

For organizations relying on cloud-native development workflows, this represents a significant escalation in supply chain threats.

In this deep dive, we’ll explore:

How malicious Next.js repositories infect developer machines
The multi-stage execution chain used in the campaign
Real-world risk to enterprise environments
Detection and threat hunting strategies
Best practices aligned with Zero Trust and NIST guidance

What Are Malicious Next.js Repositories?

At their core, these repositories appear legitimate:

Clean project structures
Functional Next.js applications
Realistic documentation
Recruitment-themed challenges

However, embedded within the project are hidden execution triggers that retrieve and execute attacker-controlled JavaScript at runtime.

This technique blends into normal developer workflows, making detection difficult.

How the Attack Campaign Works

The campaign was initially identified through suspicious outbound connections from Node.js processes on developer machines. Telemetry revealed repeated communication with known C2 IP addresses.

By correlating:

DeviceNetworkEvents
DeviceProcessEvents
Repository execution chains

Analysts traced infections back to malicious repositories hosted on platforms like Bitbucket.

Common Repository Families Identified

Microsoft Defender researchers uncovered clusters with similar naming and code patterns:

Cryptan
JP-soccer
RoyalJapan
SettleMint

Variants included tags such as:

v1
master
demo
platform
server

Shared loader logic and staging infrastructure revealed a coordinated campaign rather than isolated incidents.

Three Entry Points, One Shared Backdoor

All execution paths ultimately lead to:

Runtime retrieval and in-memory execution of attacker-controlled JavaScript.

1️⃣ VS Code Workspace Automation Abuse

When a developer opens the repository:

The .vscode/tasks.json file contains runOn: "folderOpen"
A Node.js script automatically executes
It fetches a JavaScript loader from a Vercel-hosted endpoint
The script begins beaconing to C2 infrastructure

This exploits trusted development workflows inside Visual Studio Code.

2️⃣ Trojanized npm Development Server

When developers run:

npm run dev

The project includes:

Modified assets (e.g., trojanized jquery.min.js)
Base64-encoded staging URLs
Runtime decoding and loader retrieval

The malicious script connects to the same Vercel staging infrastructure used in other infection paths.

3️⃣ Backend Server Startup Exploit

On server initialization:

A backend route decodes a base64 endpoint from a .env file
It exfiltrates full process environment variables
Cloud API keys, tokens, and credentials are transmitted
Attacker-supplied JavaScript executes via dynamic compilation

This is particularly dangerous because it directly targets environment secrets.

Multi-Stage Payload Execution

Stage 1: Host Profiling

A lightweight payload:

Profiles the system
Establishes persistence
Polls the C2 server at fixed intervals

Stage 2: Full Remote Access

Once operators engage:

Directory browsing
Sensitive file collection
Credential harvesting
Staged uploads to attacker infrastructure

At this stage, the developer machine effectively becomes a remote-controlled implant.

Why This Is a Major Enterprise Risk

Developer endpoints are high-value targets.

They often contain:

Source code repositories
Cloud API keys
Database credentials
CI/CD pipeline tokens
SSH keys
Infrastructure-as-Code templates

A single compromised developer machine can lead to:

Source code theft
Cloud environment takeover
Production credential exposure
Ransomware deployment
Supply chain poisoning

This attack model bypasses traditional perimeter defenses by embedding malicious behavior inside trusted development workflows.

Alignment with MITRE ATT&CK

The campaign maps to several MITRE ATT&CK techniques:

T1195 – Supply Chain Compromise
T1059 – Command and Scripting Interpreter
T1027 – Obfuscated Files or Information
T1105 – Ingress Tool Transfer
T1071 – Application Layer Protocol

Understanding these mappings helps SOC teams design better detection strategies.

Detection & Threat Hunting Guidance

Security teams should monitor for:

Suspicious Node.js Activity

Unusual outbound connections
Connections to staging endpoints (e.g., Vercel)
Node processes initiating unexpected network traffic

Key Telemetry Sources

DeviceNetworkEvents
DeviceProcessEvents
Identity risk alerts
Cloud audit logs

Hunting Query Focus Areas

Node.exe spawning external connections
Base64-decoded network strings
Workspace-triggered automation execution

Any unusual Node.js outbound communication from developer machines should be investigated immediately.

Best Practices to Protect Development Teams

1️⃣ Enable VS Code Workspace Trust

Use Restricted Mode for unknown folders
Disable automatic task execution
Enforce policy-based configuration

2️⃣ Apply Attack Surface Reduction (ASR) Rules

Block:

Obfuscated script execution
Suspicious child process creation
Credential dumping techniques

3️⃣ Strengthen Identity Security

Enforce Conditional Access
Require phishing-resistant MFA
Monitor risky sign-ins

4️⃣ Protect Secrets Properly

Avoid storing:

Production credentials on dev machines
Long-lived API keys
Static cloud tokens

Instead:

Use short-lived credentials
Implement secret managers
Enforce least privilege

5️⃣ Adopt Zero Trust for Developers

Zero Trust must apply to:

Code execution
Repository cloning
Dev workstation access
Cloud resource usage

Trusting code because it “looks legitimate” is no longer acceptable.

Common Misconceptions

❌ “If it’s on Bitbucket or GitHub, it’s safe.”
Public repositories can be weaponized.

❌ “It’s just a frontend project.”
Malicious JavaScript can execute system-level commands.

❌ “Our EDR will catch it.”
In-memory loaders and staged payloads evade basic signature detection.

Compliance & Governance Considerations

This campaign impacts organizations subject to:

NIST SP 800-53 (System Integrity Controls)
ISO/IEC 27001 (Secure Development Practices)
SOC 2 (Change and Access Controls)
GDPR (Data protection obligations)

Failure to secure development endpoints may lead to:

Intellectual property loss
Regulatory penalties
Contractual liability
Reputation damage

FAQs

1. What are malicious Next.js repositories?

They are poisoned repositories disguised as legitimate projects that execute hidden backdoors when developers clone and run them.

2. How do attackers gain access?

Through automatic task execution, trojanized npm scripts, or backend route manipulation that retrieves attacker-controlled payloads.

3. Why target developers?

Developer machines contain high-value credentials, source code, and cloud access tokens that enable large-scale compromise.

4. How can organizations detect this attack?

Monitor unusual Node.js outbound traffic, enable endpoint telemetry correlation, and enforce strict development environment controls.

5. Does this qualify as a supply chain attack?

Yes. It leverages software development workflows to achieve compromise, aligning with modern supply chain threat tactics.

Conclusion

The rise of malicious Next.js repositories marks a strategic evolution in software supply chain attacks.

Rather than compromising package managers or CI/CD systems, attackers are going directly after developers — the individuals with the keys to cloud infrastructure and intellectual property.

For security leaders, the priority is clear:

Harden developer endpoints
Monitor Node.js execution chains
Enforce Zero Trust principles
Protect secrets aggressively
Audit third-party code before execution

In modern cybersecurity, code execution equals access.

And in the hands of attackers, even a simple npm run dev can become the start of a full-scale breach.