CVE-2023-4961: Stored Cross-Site Scripting Vulnerability in Poptin WordPress Plugin

The popular Poptin plugin for WordPress has been identified as having a Stored Cross-Site Scripting (XSS) vulnerability in versions up to and including 1.3. The vulnerability affects the 'poptin-form' shortcode, and is due to insufficient input sanitization and output escaping on user-supplied attributes. This makes it possible for authenticated attackers with contributor-level or higher permissions to inject arbitrary web scripts into pages. These injected scripts will then execute whenever a user accesses the infected page.

Code Snippet and Exploit Details

The vulnerability lies in the Poptin plugin's handling of shortcode attributes. When a user with contributor-level or higher permissions adds a shortcode with the 'poptin-form' attribute, the input is not properly sanitized nor is the output escaped. This allows an attacker to inject malicious JavaScript code as an attribute of the 'poptin-form' shortcode.

For example, the following malicious shortcode could be inserted into a WordPress page

[poptin-form id="123" example_attribute="<script>alert('XSS')</script>"]

When a user visits the page with this shortcode, the JavaScript code within the 'example_attribute' will be executed, potentially leading to malicious actions, such as stealing user cookies or session tokens.

Original References

The vulnerability was discovered and reported by researcher. Their findings and analysis, along with proof-of-concept (PoC) code and demonstration of the vulnerability, can be found in the original report.

GitHub Repository of Poptin plugin: https://github.com/poptin/poptin

Impact, Mitigation, and Recommendations

This vulnerability poses a serious risk to website owners and users, as attackers can take advantage of the flaw to perform attacks ranging from stealing sensitive data to complete takeover of the WordPress website.

The Poptin plugin developers have been notified of the vulnerability and have released a patch to address the issue. WordPress users using the Poptin plugin are advised to update to the latest version immediately to mitigate the risk associated with this vulnerability.

Limiting contributor-level roles on your WordPress instance to trusted users only.

- Ensuring that other WordPress plugins used on your site are regularly updated and free from known vulnerabilities.
- Implementing Content Security Policy (CSP) headers on your WordPress site to limit the potential impact of XSS vulnerabilities.

Conclusion

Administrators should be aware of the risks associated with using older, unsupported versions of the Poptin plugin and must update to new versions immediately after they are released. By doing so, site owners will protect not only themselves but also visitors from potential attacks due to CVE-2023-4961.

Timeline

Published on: 10/20/2023 08:15:12 UTC
Last modified on: 11/07/2023 04:23:13 UTC