Windows Defender Ulthar.A!ml alert on Superpowers install (apparent false positive)

[nlpromptbuilders]

When downloading the latest superpowers skill, windows defender for endpoint triggers a Virus Detected alert.
The detected malware is: Trojan:Script/Ulthar.A!ml

This could be a supply-chain attack of some sort!
Please investigate!!

[obra]

@nlpromptbuilders
Hi, Can you tell us exactly what you're seeing? Where and how did you try to install Superpowers? Which harness are you using? What commands did you type? I'd like to try to repro this as quickly as possible.

[arittr]

Thanks for the report — we've dug into this in depth. Here's what we found, and one thing we need from you to finish running it down.

What we checked:

• Full audit of the v6.3.0 tree. No shipped script makes network calls, contains encoded payloads, or touches any persistence mechanism. The only Windows-executable file in the plugin is hooks/run-hook.cmd, a small batch wrapper that finds Git-for-Windows bash to run hook scripts — and it has been byte-identical for 16 consecutive releases, since v4.3.1 in February. Nothing Windows-executable changed in v6.3.0.
• VirusTotal: both the wrapper and the complete v6.3.0 source zip scan clean — zero detections across ~61 engines, including Microsoft's:
  • run-hook.cmd: https://www.virustotal.com/gui/file/d3d9c6199678dab2858e60509dde5e7414f13c2a2b5e48a38b1d368b6e1d6abb
  • v6.3.0 zip: https://www.virustotal.com/gui/file/3d4b48b75d6ea46047183b73938088cbf22196518b3c46873446a5ff11b02104
• The detection name itself: the !ml suffix indicates the verdict came from Defender's cloud machine-learning models rather than a signature match. Those models err on the side of caution with unsigned scripts, and there are documented cases where Microsoft reviewed files flagged as Trojan:Script/Ulthar.A!ml and removed the detection after determining they were clean (LibreDiagnostics in Feb 2026, Win11Debloat in Jun 2026, among others).

So our best read is that this is the ML model being cautious about an unsigned script bundle — but we're not assuming that. We'd like to identify the exact file your alert names so we can submit that specific artifact to Microsoft for review.

Could you run this in PowerShell on the affected machine and paste the output?

Get-MpThreatDetection | Where-Object ThreatName -match Ulthar |
  Format-List ThreatName, Resources, InitialDetectionTime, ProcessName

Resources is the exact file path Defender flagged. If PowerShell isn't convenient: Windows Security → Virus & threat protection → Protection history → open the alert → "Affected items" shows the same path. And since you're on Defender for Endpoint, whoever manages your security portal can also pull the flagged path and SHA-256 from the alert's evidence tab.

Also helpful: the exact way you installed (which harness and command — e.g. Claude Code /plugin install, a git clone, or a zip downloaded in a browser), and whether the alert fired during the download itself or at install/first run.

Once we have the flagged path/hash, we'll submit it to Microsoft's false-positive portal for a definitive verdict — in the cases above that took about 48 hours. If Defender quarantined files on your machine, your security team can restore them and add an allow indicator once Microsoft confirms, or simply wait for the verdict.

[nlpromptbuilders]

When I download the full zip for the latest version 6.3.0. The 6.2.0 version has no malware embedded. The exact malware detected in the 6.3.0 version is: Trojan:Script/Ulthar.A!mlOp 13 aug 2026 om 20:06 heeft Jesse Vincent ***@***.***> het volgende geschreven:obra left a comment (obra/superpowers#2143) @nlpromptbuilders Hi, Can you tell us exactly what you're seeing? Where and how did you try to install Superpowers? Which harness are you using? What commands did you type? I'd like to try to repro this as quickly as possible. —Reply to this email directly, view it on GitHub, or unsubscribe.You are receiving this because you were mentioned.Message ID: ***@***.***>

[arittr]

When I download the full zip for the latest version 6.3.0

Download from where? The repo itself? What harness are you trying to install into?