# [CRIT] lightning PyPI Compromise: A Bun-Based Credential Stealer in Python

**Source:** Snyk
**Published:** 2026-04-30
**Article:** https://snyk.io/blog/lightning-pypi-compromise-bun-based-credential-stealer/

## Threat Profile

Snyk Blog In this article
Written by Stephen Thoemmes 
April 30, 2026
0 mins read On April 30, 2026, two malicious releases of the popular lightning PyPI package were published, affecting the deep learning framework formerly distributed as pytorch-lightning . Versions 2.6.2 and 2.6.3 ship a hidden _runtime directory that downloads the Bun JavaScript runtime from GitHub at import time and uses it to execute an ~11 MB obfuscated credential stealer. The last clean release is 2.6.1 , published Janua…

## Indicators of Compromise (high-fidelity only)

- **Domain (defanged):** `22evxpggnkyrxpluewqsrv5j4jtde6hut2peq3w44d6ase676qlkoead.onion`
- **SHA256:** `8046a11187c135da6959862ff3846e99ad15462d2ec8a2f77a30ad53ebd5dcf2`
- **SHA256:** `5f5852b5f604369945118937b058e49064612ac69826e0adadca39a357dfb5b1`
- **SHA256:** `56070a9d8de0c0ffb1ec5c309953cf4679432df5a78df9aeb020fbb73d2be9fb`
- **SHA1:** `f1b3e7b3eec3294c4d6b5f87854a52471f03997f`
- **MD5:** `40d0f21b64ec8fb3a7a1959897252e09`

## MITRE ATT&CK Techniques

- **T1528** — Steal Application Access Token
- **T1098.001** — Account Manipulation: Additional Cloud Credentials
- **T1566.002** — Spearphishing Link
- **T1204.001** — User Execution: Malicious Link
- **T1059.001** — PowerShell
- **T1204.004** — User Execution: Malicious Copy and Paste
- **T1027** — Obfuscated Files or Information
- **T1195.002** — Compromise Software Supply Chain
- **T1071** — Application Layer Protocol
- **T1204.002** — User Execution: Malicious File
- **T1059.006** — Command and Scripting Interpreter: Python
- **T1105** — Ingress Tool Transfer
- **T1195.001** — Compromise Software Dependencies and Development Tools
- **T1098** — Account Manipulation
- **T1567** — Exfiltration Over Web Service

## Kill chain phases observed

_(none detected from narrative keywords)_

## Recommended hunts

### lightning PyPI compromise artifacts: start.py / router_runtime.js write

`UC_343_8` · phase: **install** · confidence: **Medium** · AI-generated for this article

**Splunk SPL (CIM):**
```spl
| tstats summariesonly=true count min(_time) as firstTime max(_time) as lastTime values(Filesystem.file_name) as file_name values(Filesystem.file_path) as file_path values(Filesystem.file_hash) as file_hash values(Filesystem.user) as user from datamodel=Endpoint.Filesystem where (Filesystem.file_hash IN ("8046a11187c135da6959862ff3846e99ad15462d2ec8a2f77a30ad53ebd5dcf2","5f5852b5f604369945118937b058e49064612ac69826e0adadca39a357dfb5b1","56070a9d8de0c0ffb1ec5c309953cf4679432df5a78df9aeb020fbb73d2be9fb")) OR ((Filesystem.file_name="start.py" OR Filesystem.file_name="router_runtime.js") AND (Filesystem.file_path="*\\lightning\\_runtime\\*" OR Filesystem.file_path="*/lightning/_runtime/*")) by Filesystem.dest Filesystem.file_path Filesystem.file_name Filesystem.file_hash | `drop_dm_object_name(Filesystem)` | convert ctime(firstTime) ctime(lastTime)
```

**Defender KQL:**
```kql
DeviceFileEvents
| where Timestamp > ago(30d)
| where ActionType in ("FileCreated","FileModified","FileRenamed")
| where SHA256 in~ (
    "8046a11187c135da6959862ff3846e99ad15462d2ec8a2f77a30ad53ebd5dcf2",
    "5f5852b5f604369945118937b058e49064612ac69826e0adadca39a357dfb5b1",
    "56070a9d8de0c0ffb1ec5c309953cf4679432df5a78df9aeb020fbb73d2be9fb"
  )
  or (FileName in~ ("start.py","router_runtime.js")
      and (FolderPath has @"\lightning\_runtime\" or FolderPath has "/lightning/_runtime/"))
| project Timestamp, DeviceName, FileName, FolderPath, SHA256,
          InitiatingProcessFileName, InitiatingProcessCommandLine, InitiatingProcessAccountName
| order by Timestamp desc
```

### Python child process executing lightning _runtime/start.py bootstrapper

`UC_343_9` · phase: **install** · confidence: **High** · AI-generated for this article

**Splunk SPL (CIM):**
```spl
| tstats summariesonly=true count min(_time) as firstTime max(_time) as lastTime values(Processes.process) as process values(Processes.process_path) as process_path values(Processes.parent_process_name) as parent_process_name values(Processes.user) as user from datamodel=Endpoint.Processes where Processes.process_name IN ("python.exe","pythonw.exe","python","python3","python3.exe") AND (Processes.process="*lightning\\_runtime\\start.py*" OR Processes.process="*lightning/_runtime/start.py*") by Processes.dest Processes.process_name Processes.parent_process_name | `drop_dm_object_name(Processes)` | convert ctime(firstTime) ctime(lastTime)
```

**Defender KQL:**
```kql
DeviceProcessEvents
| where Timestamp > ago(30d)
| where FileName in~ ("python.exe","pythonw.exe","python","python3","python3.exe")
| where ProcessCommandLine matches regex @"(?i)lightning[\\/]_runtime[\\/]start\.py"
| project Timestamp, DeviceName, AccountName,
          ParentImage = InitiatingProcessFolderPath,
          ParentCmd = InitiatingProcessCommandLine,
          ChildImage = FolderPath,
          ChildCmd = ProcessCommandLine,
          SHA256
| order by Timestamp desc
```

### Shai-Hulud style repository poisoning — .claude/router_runtime.js drop

`UC_343_10` · phase: **actions** · confidence: **High** · AI-generated for this article

**Splunk SPL (CIM):**
```spl
| tstats summariesonly=true count min(_time) as firstTime max(_time) as lastTime values(Filesystem.file_path) as file_path values(Filesystem.file_name) as file_name values(Filesystem.user) as user from datamodel=Endpoint.Filesystem where Filesystem.action IN ("created","modified") AND (Filesystem.file_path="*\\.claude\\router_runtime.js" OR Filesystem.file_path="*/.claude/router_runtime.js" OR Filesystem.file_path="*\\.claude\\setup.mjs" OR Filesystem.file_path="*/.claude/setup.mjs" OR Filesystem.file_path="*\\.vscode\\setup.mjs" OR Filesystem.file_path="*/.vscode/setup.mjs" OR Filesystem.file_path="*\\.github\\workflows\\format-check.yml" OR Filesystem.file_path="*/.github/workflows/format-check.yml") by Filesystem.dest Filesystem.file_path Filesystem.file_name | `drop_dm_object_name(Filesystem)` | convert ctime(firstTime) ctime(lastTime)
```

**Defender KQL:**
```kql
DeviceFileEvents
| where Timestamp > ago(30d)
| where ActionType in ("FileCreated","FileModified")
| where (FolderPath has @"\.claude\" and FileName in~ ("router_runtime.js","setup.mjs","settings.json"))
    or (FolderPath has "/.claude/" and FileName in~ ("router_runtime.js","setup.mjs","settings.json"))
    or (FolderPath has @"\.vscode\" and FileName =~ "setup.mjs")
    or (FolderPath has "/.vscode/" and FileName =~ "setup.mjs")
    or (FolderPath has @"\.github\workflows\" and FileName =~ "format-check.yml")
    or (FolderPath has "/.github/workflows/" and FileName =~ "format-check.yml")
| project Timestamp, DeviceName, FileName, FolderPath, SHA256,
          InitiatingProcessFileName, InitiatingProcessCommandLine, InitiatingProcessAccountName
| order by Timestamp desc
```

### OAuth consent / suspicious app grant

`UC_OAUTH_ABUSE` · phase: **actions** · confidence: **High**

**Splunk SPL (CIM):**
```spl
| tstats `summariesonly` count min(_time) as firstTime max(_time) as lastTime
    from datamodel=Authentication.Authentication
    where Authentication.action="success"
      AND Authentication.signature IN (
        "Consent to application",
        "Add app role assignment grant to user",
        "Add OAuth2PermissionGrant",
        "Add delegated permission grant")
    by Authentication.user, Authentication.app, Authentication.src, Authentication.signature
| `drop_dm_object_name(Authentication)`
```

**Defender KQL:**
```kql
CloudAppEvents
| where Timestamp > ago(7d)
| where ActionType in ("Consent to application.","Add OAuth2PermissionGrant.","Add delegated permission grant.")
| project Timestamp, AccountObjectId, AccountDisplayName, ActivityType,
          ActivityObjects, IPAddress, UserAgent
```

### Phishing-link click correlated to endpoint execution

`UC_PHISH_LINK` · phase: **delivery** · confidence: **High**

**Splunk SPL (CIM):**
```spl
``` Phishing-link click that drives endpoint execution within 60s ```
| tstats `summariesonly` earliest(_time) AS click_time
    from datamodel=Web
    where Web.action="allowed"
    by Web.src, Web.user, Web.dest, Web.url
| `drop_dm_object_name(Web)`
| rename user AS recipient, dest AS clicked_domain, url AS clicked_url
| join type=inner recipient
    [| tstats `summariesonly` count
         from datamodel=Email.All_Email
         where All_Email.action="delivered" AND All_Email.url!="-"
         by All_Email.recipient, All_Email.src_user, All_Email.url, All_Email.subject
     | `drop_dm_object_name(All_Email)`
     | rex field=url "https?://(?<email_domain>[^/]+)"
     | rename recipient AS recipient]
| join type=inner src
    [| tstats `summariesonly` earliest(_time) AS exec_time
         values(Processes.process) AS exec_cmd, values(Processes.process_name) AS exec_proc
         from datamodel=Endpoint.Processes
         where Processes.parent_process_name IN ("chrome.exe","msedge.exe","firefox.exe",
                                                   "outlook.exe","brave.exe","arc.exe")
           AND Processes.process_name IN ("powershell.exe","pwsh.exe","cmd.exe","mshta.exe",
                                            "rundll32.exe","regsvr32.exe","wscript.exe",
                                            "cscript.exe","bitsadmin.exe","certutil.exe",
                                            "curl.exe","wget.exe")
         by Processes.dest, Processes.user
     | `drop_dm_object_name(Processes)`
     | rename dest AS src]
| eval delta_sec = exec_time - click_time
| where delta_sec >= 0 AND delta_sec <= 60
| table click_time, exec_time, delta_sec, recipient, src, src_user, subject,
        clicked_domain, clicked_url, exec_proc, exec_cmd
| sort - click_time
```

**Defender KQL:**
```kql
// Phishing-link click that drives endpoint execution within 60s.
// Far higher fidelity than "every clicked URL" — most legitimate clicks
// never spawn a non-browser child process, so the join eliminates the
// 99% of noise that makes a raw click query unactionable.
let LookbackDays = 7d;
let SuspectClicks = UrlClickEvents
    | where Timestamp > ago(LookbackDays)
    | where AccountName !endswith "$"
    | where ActionType in ("ClickAllowed","ClickedThrough")
    | join kind=inner (
        EmailEvents
        | where Timestamp > ago(LookbackDays)
        | where DeliveryAction == "Delivered"
        | where EmailDirection == "Inbound"
        | project NetworkMessageId, Subject, SenderFromAddress, SenderFromDomain,
                  RecipientEmailAddress, EmailTimestamp = Timestamp
      ) on NetworkMessageId
    | join kind=leftouter (
        EmailUrlInfo | project NetworkMessageId, Url, UrlDomain
      ) on NetworkMessageId, Url
    | project ClickTime = Timestamp, AccountUpn, IPAddress, Url, UrlDomain,
              Subject, SenderFromAddress, SenderFromDomain, RecipientEmailAddress,
              ActionType;
// Correlate to a non-browser child process spawned within 60 seconds on
// the recipient's device.
DeviceProcessEvents
| where Timestamp > ago(LookbackDays)
| where InitiatingProcessFileName in~ ("chrome.exe","msedge.exe","firefox.exe",
                                         "outlook.exe","brave.exe","arc.exe")
| where FileName in~ ("powershell.exe","pwsh.exe","cmd.exe","mshta.exe",
                        "rundll32.exe","regsvr32.exe","wscript.exe","cscript.exe",
                        "bitsadmin.exe","certutil.exe","curl.exe","wget.exe")
| join kind=inner SuspectClicks on $left.AccountName == $right.AccountUpn
| where Timestamp between (ClickTime .. ClickTime + 60s)
| project ClickTime, ProcessTime = Timestamp,
          DelaySec = datetime_diff('second', Timestamp, ClickTime),
          DeviceName, AccountName, RecipientEmailAddress, SenderFromAddress,
          Subject, Url, UrlDomain, ActionType,
          FileName, ProcessCommandLine, InitiatingProcessFileName
| order by ClickTime desc
```

### Fake CAPTCHA / clipboard-injected PowerShell (ClickFix / FakeCaptcha)

`UC_FAKECAPTCHA` · phase: **exploit** · confidence: **High**

**Splunk SPL (CIM):**
```spl
| tstats `summariesonly` count min(_time) as firstTime max(_time) as lastTime
    from datamodel=Endpoint.Processes
    where Processes.parent_process_name IN ("explorer.exe","RuntimeBroker.exe")
      AND Processes.process_name IN ("powershell.exe","pwsh.exe","mshta.exe")
      AND (Processes.process="*iex*" OR Processes.process="*Invoke-Expression*"
        OR Processes.process="*FromBase64*" OR Processes.process="*DownloadString*"
        OR Processes.process="*hxxp*" OR Processes.process="*curl*" OR Processes.process="*wget*")
    by Processes.dest, Processes.user, Processes.process, Processes.parent_process_name
| `drop_dm_object_name(Processes)`
```

**Defender KQL:**
```kql
DeviceProcessEvents
| where Timestamp > ago(7d)
| where AccountName !endswith "$"
| where InitiatingProcessFileName in~ ("explorer.exe","RuntimeBroker.exe")
| where FileName in~ ("powershell.exe","pwsh.exe","mshta.exe")
| where ProcessCommandLine matches regex @"(?i)(iex|invoke-expression|frombase64|downloadstring|hxxp|curl |wget )"
| project Timestamp, DeviceName, AccountName, ProcessCommandLine, InitiatingProcessCommandLine
```

### PowerShell encoded / obfuscated command

`UC_PS_OBFUSCATED` · phase: **exploit** · confidence: **High**

**Splunk SPL (CIM):**
```spl
| tstats `summariesonly` count min(_time) as firstTime max(_time) as lastTime
    from datamodel=Endpoint.Processes
    where Processes.process_name IN ("powershell.exe","pwsh.exe")
      AND (Processes.process="*-enc *" OR Processes.process="*EncodedCommand*"
        OR Processes.process="*FromBase64String*" OR Processes.process="*-nop*"
        OR Processes.process="*-w hidden*" OR Processes.process="*Invoke-Expression*"
        OR Processes.process="*IEX(*" OR Processes.process="*DownloadString*"
        OR Processes.process="*Net.WebClient*")
    by Processes.dest, Processes.user, Processes.process_name, Processes.process, Processes.parent_process_name
| `drop_dm_object_name(Processes)`
```

**Defender KQL:**
```kql
DeviceProcessEvents
| where Timestamp > ago(7d)
| where AccountName !endswith "$"
| where FileName in~ ("powershell.exe","pwsh.exe")
| where ProcessCommandLine matches regex @"(?i)(-enc|encodedcommand|frombase64string|-nop|-w\s+hidden|invoke-expression|iex\s*\(|downloadstring|net\.webclient)"
| project Timestamp, DeviceName, AccountName, ProcessCommandLine,
          InitiatingProcessFileName, InitiatingProcessCommandLine
```

### Trusted vendor binary / installer launching unusual children

`UC_SUPPLY_CHAIN` · phase: **exploit** · confidence: **Medium**

**Splunk SPL (CIM):**
```spl
| tstats `summariesonly` count min(_time) as firstTime max(_time) as lastTime
    from datamodel=Endpoint.Processes
    where Processes.parent_process_name IN ("setup.exe","installer.exe","update.exe")
      AND Processes.process_name IN ("powershell.exe","cmd.exe","rundll32.exe","regsvr32.exe","mshta.exe","wscript.exe","cscript.exe","wmic.exe","bitsadmin.exe")
    by Processes.dest, Processes.user, Processes.parent_process_name, Processes.process_name, Processes.process
| `drop_dm_object_name(Processes)`
```

**Defender KQL:**
```kql
DeviceProcessEvents
| where Timestamp > ago(7d)
| where AccountName !endswith "$"
| where InitiatingProcessFileName in~ ("setup.exe","installer.exe","update.exe")
| where FileName in~ ("powershell.exe","cmd.exe","rundll32.exe","regsvr32.exe","mshta.exe","wscript.exe","cscript.exe","wmic.exe","bitsadmin.exe")
| project Timestamp, DeviceName, AccountName, InitiatingProcessFileName, FileName, ProcessCommandLine
```

### Article-specific behavioural hunt — lightning PyPI Compromise: A Bun-Based Credential Stealer in Python

`UC_343_7` · phase: **exploit** · confidence: **High**

**Splunk SPL (CIM):**
```spl
``` Article-specific bespoke detection — lightning PyPI Compromise: A Bun-Based Credential Stealer in Python ```
| tstats `summariesonly` count earliest(_time) AS firstTime latest(_time) AS lastTime
    from datamodel=Endpoint.Processes
    where (Processes.process_name IN ("start.py","router_runtime.js","__init__.py","execution.js"))
    by Processes.dest, Processes.user, Processes.process_name,
       Processes.process, Processes.parent_process_name, Processes.process_path
| `drop_dm_object_name(Processes)`
| `security_content_ctime(firstTime)`
| append [
| tstats `summariesonly` count
    from datamodel=Endpoint.Filesystem
    where Filesystem.action IN ("created","modified")
      AND (Filesystem.file_name IN ("start.py","router_runtime.js","__init__.py","execution.js"))
    by Filesystem.dest, Filesystem.user, Filesystem.process_name,
       Filesystem.file_path, Filesystem.file_name
| `drop_dm_object_name(Filesystem)`
]
```

**Defender KQL:**
```kql
// Article-specific bespoke detection — lightning PyPI Compromise: A Bun-Based Credential Stealer in Python
// Hunts the actual binaries / paths / commandline fragments named
// in the article instead of a generic technique-class template.
DeviceProcessEvents
| where Timestamp > ago(30d)
| where (FileName in~ ("start.py", "router_runtime.js", "__init__.py", "execution.js"))
| project Timestamp, DeviceName, AccountName, FileName,
          FolderPath, ProcessCommandLine,
          InitiatingProcessFileName, InitiatingProcessCommandLine
| order by Timestamp desc

// File-creation events for the named binaries / paths
DeviceFileEvents
| where Timestamp > ago(30d)
| where ActionType in ("FileCreated","FileModified")
| where (FileName in~ ("start.py", "router_runtime.js", "__init__.py", "execution.js"))
| project Timestamp, DeviceName, AccountName, FolderPath,
          FileName, ActionType, InitiatingProcessFileName,
          InitiatingProcessCommandLine
| order by Timestamp desc
```

### IOC-driven hunts (use shared templates)

These are standard IOC-substitution hunts — the canonical SPL and KQL live once in [`_TEMPLATES.md`](../_TEMPLATES.md), so we don't repeat the same boilerplate on every CVE / hash / network-IOC briefing.

- **Network connections to article IPs / domains** ([template](../_TEMPLATES.md#network-ioc)) — phase: **c2**, confidence: **High**
  - IP / domain IOC(s): `22evxpggnkyrxpluewqsrv5j4jtde6hut2peq3w44d6ase676qlkoead.onion`

- **File hash IOCs — endpoint file/process match** ([template](../_TEMPLATES.md#hash-ioc)) — phase: **install**, confidence: **High**
  - file hash IOC(s): `8046a11187c135da6959862ff3846e99ad15462d2ec8a2f77a30ad53ebd5dcf2`, `5f5852b5f604369945118937b058e49064612ac69826e0adadca39a357dfb5b1`, `56070a9d8de0c0ffb1ec5c309953cf4679432df5a78df9aeb020fbb73d2be9fb`, `f1b3e7b3eec3294c4d6b5f87854a52471f03997f`, `40d0f21b64ec8fb3a7a1959897252e09`


## Why this matters

Severity classified as **CRIT** based on: IOCs present, 11 use case(s) fired, 15 technique(s) inferred. Read the full article for actor attribution, tooling details, and any defanged IOCs in the body that aren't visible in the RSS summary.