"third-party[.]com has been a generic documentation placeholder for years, the same role example.com plays," Manifold Security's Head of Research, Ax Sharma, said.
That commonplace sentence describes why a single, non‑reserved placeholder domain quietly flipped from harmless example into an active weapon. Security researchers at Manifold Security say the domain third-party[.]com — hard-coded as a sample endpoint in documentation, test cases, and skills — has been serving a ClickFix lure to Windows browsers since at least June 2026 while showing innocuous or different content to other visitors. The result: more than 1,700 public GitHub repositories now point to infrastructure that attackers control.
third-party[.]com serving a ClickFix lure to Windows browsers
According to Manifold Security, visitors from Windows browsers are shown a Cloudflare check that poisons the victim's clipboard and instructs them to paste and run a command via the Windows Run dialog. The pasted command is designed to extract and run a remote PowerShell payload. When a macOS user hits the same page, the site displays a decoy error: "macOS is not supported. This website requires a Windows PC to access. Please try again from a Windows device."
ClickFix is the social engineering technique at work: web pages display error messages or verification prompts that trick users into copying and executing hidden commands via the Windows Run dialog or Terminal. Manifold's writeup notes the attack often relies on clipboard hijacking — also called pastejacking — to push malicious script into a user's clipboard for subsequent pasting.
At the time of Manifold's disclosure the domain had been marked malicious and unsafe on VirusTotal and Google's Safe Browsing list.
Exposure across 1,700+ public GitHub repositories
A GitHub search found third-party[.]com referenced in over 1,700 public repositories. Those references appear in a variety of places, including AI agent skills and MCP-server documentation that cite the domain as an example endpoint. "In every one of those places it is exactly what it looks like: a placeholder, an example, a stand‑in, and entirely reasonable use by the teams involved," Sharma said. "It is also, now, a live pointer to a ClickFix server."
Manifold's point is tactical: a static scan of files or a DNS lookup from an analysis host may not reveal the malicious content a real browser receives at request time. "You can scan the skill, read the file, resolve the domain from your analysis box, and conclude it is fine, and be completely wrong about what a Windows user's agent receives when it follows the same link," Manifold Security pointed out. "A file scan cannot see what a website decides to send. The tell only appears at request time, from the caller that matters."
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See what we buildThirteen additional placeholder domains and active scams
Manifold said it identified 13 more placeholder domains that are not IANA‑reserved. Two of those domains — yoursite[.]com and your-domain[.]com — were serving scams and scareware to macOS visitors while presenting ordinary parking pages to other users. "On a macOS browser, your-domain[.]com showed a fake 'MacOS Security Center' claiming four viruses and selling a counterfeit McAfee renewal at 55% off," security researcher Cody Nash said. "On another macOS render, yoursite[.]com showed a counterfeit ZDF news article advertising an investment scheme."
- your-domain[.]com
- yourdomain[.]com
- your-site[.]com
- yoursite[.]com
- your-app[.]com
- yourapp[.]com
- myapp[.]com
- mysite[.]com
- acme[.]com
- company[.]com
- mycompany[.]com
- vendor[.]com
- foo[.]com
Manifold noted these domains "pass static checks" and are present in hundreds of thousands of GitHub files and hundreds of agent skills — a broad exposure beyond the clipboard‑hijacking examples they observed.
Developer guidance and recommended mitigations
Manifold's core recommendation is practical and narrow: audit documentation, test cases, and skills, and treat plausible placeholder domains as squattable. Use IANA‑reserved example names — "example[.]com" (and "example[.]org," "example[.]net") — rather than plausible, descriptive placeholders like yourcompany[.]com or your-api[.]com that attackers can register and weaponize.
The firm warns that static analysis alone is insufficient. Because malicious behavior can be served only to particular user agents or at request time, developers and security teams should consider dynamic checks that emulate the browser or agent that will follow the links used in docs and skills.
What this means for developers, security teams, and end users
Developers: Replace non‑reserved placeholder domains in documentation, tests, and agent skills with IANA‑reserved example domains and audit existing repositories for live pointers.
Security teams: Add runtime or request‑time checks for URLs embedded in code and documentation, recognizing that static scans may miss content served selectively to different user agents.
End users: Be cautious of browser prompts that request copying and pasting commands into system dialogs; the ClickFix technique relies on that exact behavior to deliver a remote PowerShell payload to Windows systems.
Manifold's findings are a reminder that a small editorial convenience — using a plausible example domain — can morph into a large operational risk when the name is registered and abused. The fix is procedural: replace squattable placeholders with reserved examples, and treat any public reference as potentially live until proven otherwise.
