pretalx mail templates vulnerable to email injection via unescaped user-controlled placeholders
An unauthenticated attacker can send arbitrary HTML-rendered emails from a pretalx instance's configured sender address by embedding malformed HTML or markdown link syntax in a user-controlled template placeholder such as the account display name. The most direct vector is the password-reset flow: the attacker registers an account with a malicious name, enters the victim's email address, and triggers a password reset. The resulting email is delivered from the event's legitimate sender address and passes SPF/DKIM/DMARC validation, making it a ready-made phishing vector.
The same class of bug affects every mail template that interpolates a user-controlled placeholder (speaker name, proposal title, biography, question answers, etc.), including organiser-triggered emails such as acceptance/rejection notifications.
Credits
Thanks go to Mark Fijneman for finding and reporting a subset of this issue, which alerted us to the wider vulnerability.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | pretalx | < 2026.1.0 | 2026.1.0 |
References
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N- Weakness (CWE)
CWE-116, CWE-79- Platform
- Python (PyPI)
- Package
pretalx- Disclosed
- 18.04.2026
- Updated
- 11.10.2026 12:19
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2026-109 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-jm8c-9f3j-4378 - CC BY 4.0
Vulnerability history: pretalx
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 4
- First → latest
- 04.2023 04.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 2
- Medium 2
Disclosures per year
- 2023: 2
- 2024: 0
- 2025: 0
- 2026: 2
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