Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
discourse-bbcode is the official BBCode plugin for Discourse. Prior to commit 91478f5, CSS injection can occur when rendering content generated with the discourse-bccode plugin. This vulnerability only affects sites which have the discourse-bbcode plugin installed and enabled. This issue is patched in commit 91478f5. As a workaround, ensure that the Content Security Policy is enabled and monitor any posts that contain bbcode.
CWE-79 - Cross Site Scripting
Cross-Site Scripting, commonly referred to as XSS, is the most dominant class of vulnerabilities. It allows an attacker to inject malicious code into a pregnable web application and victimize its users. The exploitation of such a weakness can cause severe issues such as account takeover, and sensitive data exfiltration. Because of the prevalence of XSS vulnerabilities and their high rate of exploitation, it has remained in the OWASP top 10 vulnerabilities for years.