CVE-2025-48954: Discourse XSS Vulnerability via Social Logins
Discourse, a popular open-source discussion platform, is susceptible to a cross-site scripting (XSS) vulnerability affecting versions prior to 3.5.0.beta6. This flaw can be exploited when the Content Security Policy (CSP) isn't enabled while users are utilizing social login features. This blog post details the vulnerability, its impact, and how to mitigate the risk.
Vulnerability Details
- CVE ID: CVE-2025-48954
- Description: Discourse is vulnerable to cross-site scripting when the content security policy isn't enabled when using social logins. An attacker could inject malicious scripts into a user's browser session.
- CVSS Score: 8.1 (HIGH)
- CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
- CVSS Explanation: The CVSS vector indicates that this is a network-based attack (AV:N) requiring no special access privileges (PR:N). User interaction is required (UI:R), meaning a user must click a malicious link or interact with injected content. While the scope is unchanged (S:U), the impact to confidentiality (C:H) and integrity (I:H) is high, meaning an attacker could steal sensitive data and modify the website on the user's behalf. Availability impact is none (A:N).
- Exploit Requirements: A vulnerable Discourse instance with social logins enabled and CSP disabled. The attacker needs to entice a user to interact with a malicious link or content.
- Affected Vendor: Discourse
- Affected Product: Discourse
- Affected Version: Versions prior to 3.5.0.beta6
- CWE: CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
- CWE Explanation: Cross-site scripting (XSS) occurs when a web application allows untrusted data to be included in its output without proper validation or escaping. This allows attackers to inject malicious scripts that execute in the user's browser, potentially leading to account compromise, data theft, or website defacement.
Timeline of Events
- Reported: Likely reported before the CVE was assigned (details not specified in input)
- CVE Assigned: CVE-2025-48954
- Published: 2025-06-25
- Fixed: Fixed in version 3.5.0.beta6
Exploitability & Real-World Risk
XSS vulnerabilities are highly exploitable and pose a significant risk. In the context of Discourse, an attacker could potentially inject malicious JavaScript code that steals user credentials, redirects users to phishing sites, or defaces the forum. Given Discourse's popularity as a community platform, a successful exploit could affect a large number of users.
Recommendations
- Upgrade: Upgrade your Discourse instance to version 3.5.0.beta6 or later.
- Enable CSP: Ensure that the Content Security Policy (CSP) is enabled on your Discourse instance. CSP helps mitigate XSS attacks by restricting the sources from which the browser can load resources.
- Workaround: If upgrading is not immediately possible, enabling the content security policy is a viable workaround.
Technical Insight
The vulnerability likely stems from improper handling of user input during the social login process. Without proper sanitization and output encoding, malicious scripts can be injected into the rendered HTML, which are then executed by the user's browser. Enabling a strong Content Security Policy can prevent execution of untrusted scripts, thus mitigating the vulnerability.
Credit to Researcher(s)
Credit to the security researcher(s) who responsibly disclosed this vulnerability (details not specified in input, but typically found via the GitHub advisory).
References
Tags
#Discourse #XSS #CVE-2025-48954 #Security #Vulnerability #SocialLogins #ContentSecurityPolicy
Summary: Discourse versions before 3.5.0.beta6 are vulnerable to cross-site scripting (XSS) via social logins when the Content Security Policy (CSP) is disabled. Upgrade to 3.5.0.beta6 or enable CSP to mitigate the risk.
CVE ID: CVE-2025-48954
Risk Analysis: Successful exploitation could lead to widespread account compromise, data theft, defacement of the Discourse forum, and reputational damage to the forum owners and community.
Recommendation: Upgrade to Discourse version 3.5.0.beta6 or later, and ensure that the Content Security Policy (CSP) is enabled.
Timeline
- 2025-06-25: CVE-2025-48954 published.