Overview
This blog post discusses a significant cybersecurity vulnerability, classified under CVE-2025-48954, that affects the open-source discussion platform, Discourse. The vulnerability results from an improper content security policy (CSP) handling, leading to a potential cross-site scripting (XSS) attack when using social logins. This issue plagues all versions of Discourse prior to 3.5.0.beta6.
The severity of this vulnerability lies in its potential to compromise systems or lead to data leaks, impacting not just individual users but also businesses that leverage Discourse for community engagement. A successful exploit could lead to unauthorized control over data and systems, creating a serious security threat.
Vulnerability Summary
CVE ID: CVE-2025-48954
Severity: High (CVSS: 8.1)
Attack Vector: Remote
Privileges Required: None
User Interaction: Required
Impact: System compromise or data leakage
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Product | Affected Versions
Discourse | Prior to 3.5.0.beta6
How the Exploit Works
This vulnerability arises from the Discourse platform’s failure to enforce a content security policy when using social logins. An attacker can exploit this flaw by injecting malicious scripts into the webpage. When a user interacts with the infected application, the malicious script is executed, potentially leading to unauthorized access to sensitive data or control over the system.
Conceptual Example Code
Here’s a conceptual example of how an attacker might exploit this vulnerability using an HTTP request:
POST /social_login HTTP/1.1
Host: target.example.com
Content-Type: application/json
{
"callback_url": "javascript:malicious_code_here"
}In this pseudo-code, the “callback_url” contains malicious JavaScript code that can execute when the user interacts with the social login feature.
Mitigation Guidance
The recommended solution to protect against this vulnerability is to upgrade to Discourse version 3.5.0.beta6 or later, which contains a patch for the issue. If an upgrade is not immediately possible, users should ensure that the content security policy is enabled as a temporary workaround. Using Web Application Firewalls (WAF) or Intrusion Detection Systems (IDS) can also provide temporary protection against potential exploits. However, these measures should be seen as temporary fixes, and users are advised to apply the vendor patch for complete resolution of the vulnerability.