A new software supply chain threat has emerged, this time targeting developers integrating Stripe into .NET applications.
According to research published by ReversingLabs, threat actors uploaded a malicious NuGet package designed to mimic Stripe’s official library, aiming to silently steal API tokens and compromise payment environments.
The campaign signals a strategic shift: after previously targeting cryptocurrency-related packages, attackers are now pivoting toward mainstream financial services ecosystems.
What Happened?
The malicious package, named StripeApi.Net, was crafted to impersonate Stripe.net, Stripe’s legitimate .NET helper library — a package with more than 74 million downloads.
Rather than attempting to breach Stripe directly, attackers relied on typosquatting, a deceptive technique where a similarly named package is published to trick developers into downloading it.
The fake package:
- Used the same Stripe icon
- Replicated the official README (with minor naming tweaks)
- Linked to legitimate Stripe assets
- Used the name “StripePayments” as publisher
- Artificially inflated download numbers to appear trusted
At first glance, it looked authentic. But inside, the code told a different story.
How the Attack Worked
The malicious DLL copied most of the legitimate Stripe.net code to ensure applications would compile and run normally. Payments would process without issue, no visible red flags for developers.
However, researchers found that attackers modified critical initialization methods within the StripeClient class.
Once a developer initialized the library:
- The API token was silently captured
- A machine identifier (derived from the system name) was collected
- Both were exfiltrated to a Supabase backend controlled by the attacker
In short: applications would function normally, while API credentials were being stolen in the background.
This type of supply chain attack is particularly dangerous because it blends malicious logic into otherwise functional code.
Was Anyone Compromised?
The malicious package reportedly accumulated over 180,000 downloads across 506 versions. However, ReversingLabs’ investigation suggests most of these downloads were artificially generated to create legitimacy.
The package was identified quickly and removed by NuGet administrators shortly after being reported.
Investigators also examined the attacker’s Supabase backend and found no evidence of stolen API tokens, only a test entry.
While this specific campaign appears to have caused limited damage, the technique itself is highly concerning.
Why This Matters Globally
Modern software development depends heavily on third-party libraries. Developers trust open-source ecosystems like NuGet, npm, and PyPI to accelerate development.
But that trust is increasingly being weaponized.
A compromised Stripe API token could allow attackers to:
- Access customer payment data
- Manipulate transactions
- Extract financial records
- Compromise subscription billing systems
For fintech companies, SaaS providers, telecom operators, and e-commerce platforms across Africa, Europe, Asia, and the Middle East, this represents a serious operational risk.
Financial APIs are high-value targets and attackers know it.
Organizations seeking advanced cybersecurity protection and supply chain risk management can explore professional services from Saintynet Cybersecurity to strengthen their defenses against emerging third-party threats.
The Bigger Trend: Software Supply Chain Attacks
This campaign reinforces a growing pattern:
- Typosquatting attacks
- Compromised open-source packages
- Malicious updates injected into legitimate libraries
- Credential exfiltration through hidden functions
As we previously discussed in our coverage of software supply chain risks, attackers increasingly exploit developer trust rather than network perimeters.
The malicious logic in StripeApi.Net was subtle. The application worked as expected, that’s what makes it dangerous.
Developers cannot assume that a package is safe simply because:
- It appears widely downloaded
- It looks professionally branded
- It functions correctly
10 Recommended Security Actions
To reduce the risk of malicious package compromise, security teams should:
- Implement Software Composition Analysis (SCA) tools in CI/CD pipelines.
- Verify package publishers and maintainers before installation.
- Pin exact dependency versions rather than allowing automatic updates.
- Scan all third-party packages for malicious code prior to deployment.
- Use allowlists for approved libraries within enterprise environments.
- Monitor outbound traffic for suspicious data exfiltration attempts.
- Protect and rotate API keys regularly.
- Enable role-based access control (RBAC) on payment platforms.
- Train developers on typosquatting detection and supply chain threats — professional training programs are available at saintynet.com.
- Conduct regular third-party risk assessments to evaluate dependency exposure.
A Wake-Up Call for Developers
The StripeApi.Net case demonstrates how attackers are evolving beyond crypto-focused campaigns into mainstream financial ecosystems.
Even though this specific incident appears to have caused limited real-world damage, it serves as a powerful warning.
The next malicious package may not be detected as quickly.
As organizations accelerate digital transformation and cloud-native development, third-party risk must be treated as a core component of enterprise security strategy, not an afterthought.
Conclusion
The malicious StripeApi.Net NuGet package represents another chapter in the growing wave of software supply chain attacks targeting developers and financial ecosystems.
By mimicking a trusted library and silently exfiltrating API keys, attackers demonstrated how easily trust in open-source ecosystems can be exploited.
Although swift detection prevented widespread compromise, the incident underscores the urgent need for stronger dependency monitoring, developer awareness, and proactive security controls.
CyberCory will continue monitoring emerging supply chain threats and provide updates as the landscape evolves.
