flask-header-guard

Details

**Severity:** Critical

**Affected versions:** `= 1.0.0`

## Source: kam193 (d050fa5a7000088c15b40b82ace014d66f18520ff36464659c8ad6e999ee83cb)
During installation, the package attempts to exfiltrate sensitive environment variables and files, establish persistence and open a reverse shell. Additionally, the provided Flask middleware embeds a backdoor.


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Category: MALICIOUS - The campaign has clearly malicious intent, like infostealers.


Campaign: 2026-08-pygame-renderkit


Reasons (based on the campaign):


 - The package contains code to create a reverse shell, allowing an attacker to execute any commands on the victim's machine.


 - files-exfiltration


 - The package overrides the install command in setup.py to execute malicious code during installation.


 - exfiltration-env-variables


 - persistence

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Credit: [OpenSSF](https://github.com/ossf/malicious-packages) ([source](https://github.com/ossf/malicious-packages/blob/c40f765296358a44eb5f2d931a66d5d58d41caf7/osv/malicious/pypi/flask-header-guard/MAL-2026-15566.json))

**References:**
- https://bad-packages.kam193.eu/pypi/package/flask-header-guard
- https://github.com/ossf/malicious-packages/blob/c40f765296358a44eb5f2d931a66d5d58d41caf7/osv/malicious/pypi/flask-header-guard/MAL-2026-15566.json
- https://github.com/ossf/malicious-packages/blob/99ffa6ed40431db8a5e16c67408edddb4a51fe17/osv/malicious/pypi/flask-header-guard/MAL-2026-15566.json
- https://pypi.org/project/flask-header-guard/1.0.0
- https://github.com/advisories/GHSA-gmgc-w467-4xf7

Compromised versions (1)

• = 1.0.0

Any computer that installed or ran a compromised version should be considered fully compromised. Rotate every secret on that machine from a clean environment.