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In September 2026, Ukraine’s CERT-UA reported a campaign in which malicious JavaScript was injected into more than 100 compromised websites. Windows visitors who saw a fake Cloudflare verification prompt were told to run a command that launched a remote MSI installer, leading to LUNEXSTEALER. The warning is straightforward: a CAPTCHA or Cloudflare check should never ask you to open Run, PowerShell, or Command Prompt and execute a command.
What happened in the UAC-0277 campaign?
CERT-UA, Ukraine’s government computer incident response team, analyzed a campaign it tracked as UAC-0277. Contemporaneous coverage dates the analysis to September 30, 2026. During September, analysts identified more than 100 compromised websites carrying malicious JavaScript. That figure counts websites—not infected people or computers. The reviewed accounts do not state how many victims there were, which sectors were affected, or who was behind the campaign.
The injected script reportedly reads configuration from a smart contract on Polygon or Ethereum. Depending on that configuration, it can track visits or display a fake verification page. The contract addresses were not published in the reporting summarized here.
Why might different visitors see different pages?
The reported lure is selective: it appears to target visitors using Windows who arrive through a search-engine link, and who have not seen the page more than twice in the previous 12 hours. A person opening the same site directly, or using a different operating system, may therefore see no fake check. Not seeing the prompt does not establish that a website is safe; the site itself may have been compromised.
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How can you tell whether a Cloudflare check is fake?
The fake page imitates Cloudflare’s “I’m not a robot” verification, then tells the visitor to open the Windows Run dialog or a command shell and run a command. In the analyzed examples, that command launched msiexec.exe with a remote MSI installer URL. CERT-UA’s reporting characterizes this social-engineering approach as ClickFix: the attacker persuades the target to perform an action that starts the infection.
A warning reproduced by UNN on October 6, 2026 and attributed to Ukraine’s State Service of Special Communications and Information Protection puts it plainly: “no genuine CAPTCHA or Cloudflare will ask you to open Win+R, PowerShell, or paste commands.” If a verification prompt asks you to do that, stop and close the page—even if you recognize the website.
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The reporting describes the MSI execution as the delivery step. It does not establish that simply viewing the page installs LUNEXSTEALER; the prompt’s dangerous instruction is to run the command.
Do these 3 things before closing this tab:
1Clear out junk files and repair common Windows errors2Fix the driver behind crashes, sound loss and screen glitches3Repair Windows errors before they cause bigger problemsWhat are the three reported installation variants?
CERT-UA’s analysis describes three MSI variants. Each ultimately leads to LUNEXSTEALER, but the routes and evasion methods differ.
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| Variant | What the MSI does | Reported method | Outcome |
|---|---|---|---|
| Direct installation | Installs the payload directly. | No additional evasion step is described for this variant. | LUNEXSTEALER is installed. |
| Vulnerable-driver chain | Attempts to bypass Windows User Account Control, adds Microsoft Defender exclusions, and drops AMD’s PDFWKRNL.sys driver. |
The loader exploits CVE-2023-20598 to interfere with security tools before launching the payload. | LUNEXSTEALER is launched. |
| DLL side-loading | Drops FnHotkeyUtility.exe and a malicious spkvol.dll. |
The executable loads the malicious library, which decrypts and launches the payload. | LUNEXSTEALER is launched. |
What the AMD driver detail means
The technical account describes CVE-2023-20598 as improper privilege management in AMD’s pdfwkrnl.sys kernel driver. It reports an NVD CVSS 3.1 score of 7.8 and says AMD fixed the issue in Adrenalin Edition 23.9.2 and PRO Edition 23.Q4. These version and severity details are reported by that campaign analysis.
This is a bring-your-own-vulnerable-driver (BYOVD) technique: an attacker attempts to load a vulnerable signed driver as part of the attack. Having an up-to-date AMD driver installed does not, on its own, address an attempt to bring and load a vulnerable driver. Administrators should verify that the vulnerable-driver blocklist is covered by the policy actually deployed in their environment.
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What can LUNEXSTEALER do?
The analysis describes LUNEXSTEALER as a 64-bit Windows information stealer that can also execute remote tasks. Reported targets include passwords and tokens stored by browsers, cryptocurrency wallet data, desktop applications, and system information.
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Depending on the server’s configuration, an infected system may also receive the LUNARAXE browser extension and NAIVEMESS. The extension can appear under the name “Microsoft Office Word Editor,” while NAIVEMESS provides filesystem access to the extension. The analysis does not say every infected device receives these additional components.
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What should you do if you encounter the prompt or ran its command?
If you have not run anything
- Do not open Run, PowerShell, or Command Prompt to follow the page’s instructions, and do not paste or execute the requested command.
- Close the page. CERT-UA’s reported recommendation applies even when the site is familiar, because a legitimate site can be compromised.
If you already ran the command
- Contact your organization’s security team or an incident-response provider and follow its containment process. SOC Prime’s guidance recommends isolating affected hosts when suspicious MSI execution or unauthorized extensions are detected.
- Tell responders what happened and when, and preserve relevant information for their investigation. Do not treat the absence of a visible browser extension as proof that the system is clean.
If you administer affected systems
- Review suspicious
msiexec.exeactivity involving remote URLs and investigate any unauthorized browser extensions. - Consider SOC Prime’s recommendations to restrict access to Win+R through policy, limit MSI installation privileges, enable Microsoft’s vulnerable-driver blocklist, and allowlist browser extensions.
- Check any proposed detection indicators against the official advisory before deploying them. The reporting contains an inconsistent spelling of a scheduled-task name, so copying that indicator directly into a production rule could create a detection error.
How can a site owner respond?
The reports say CERT-UA asks to be notified about the campaign and offers site owners help investigating a compromise. If your website is displaying a suspicious verification prompt, treat the behavior as a possible site compromise and seek help through CERT-UA’s official reporting channels. The reviewed accounts do not provide a specific reporting URL here.
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