usd-2023-0013 | Reflected XSS in SuperWebMailer

Advisory ID: usd-2023-013
Product: SuperWebMailer
Affected Version:
Vulnerability Type: CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Security Risk: MEDIUM
Vendor URL:
Vendor acknowledged vulnerability: No
Vendor Status: Not fixed
CVE number: CVE-2023-38194
CVE Link:


SuperWebMailer is an online application for managing e-mail newsletters.
An unauthenticated Cross-Site Scripting (XSS) vulnerability was discovered during an engagement.
In an XSS attack, a potentially malicious script is injected into a website.

The keepalive.php script is vulnerable to reflected XSS payloads.
The script outputs a caller GET parameter inside the HTML with insufficient encoding or filtering being applied.
Consequently, on submitting an XSS payload, it is executed.

Proof of Concept

The following request includes JavaScript in the caller parameter:

GET /keepalive.php?caller="><img+src%3d1+onerror%3dalert(document.cookie)+/>&uq_mt=1664137650.085 HTTP/2
Cookie: PHPSESSID=8k8n7rmlnugo73d3jjtaeantft; SuperWebMailer=161kd4lr0kv8qplkknm927u0cs; smlswmCsrfToken=20mqIe2UqIA2ya6ImiqaYM2Q6EuYy6y6ya2QUa
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Firefox/102.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate

As the following screenshot indicates, the above JavaScript is embedded within the application and executed:
Browser screenshot showing the executed payload


It is recommended to treat all input on the website as potentially dangerous. Hence, all output that is dynamically generated based on user-controlled data should be encoded according to its context.



  • 2022-09-26: This vulnerability was discovered by Florian Dewald and Gerbert Roitburd of usd AG.
  • 2023-04-20: First contact request via
  • 2023-05-08: Reminder sent via and contact form.
  • 2023-05-15: Second reminder to and
  • 2023-05-25: Another reminder sent to, and
  • 2023-06-05: Once more tried to inform the company of the vulnerabilities via the feedback form (
  • 2023-07-17: Sent another email to,, and, stressing that CVEs are assigned to the vulnerabilities and disclosure may happen in case we do not receive an answer soon.
  • 2023-08-17: As the vulnerabilities were found during a pentest, the customer was asked whether or not the Responsible Disclosure Team should move forward without the software vendor's cooperation.
  • 2023-10-02: Final notice given to info@superwebmailer, warning of immenent disclosure should there be no response within a week.
  • 2023-10-20: Vulnerabilities disclosed by usd AG.


This security vulnerability was identified by Florian Dewald and Gerbert Roitburd of usd AG.