The vulnerability is a stored cross‑site scripting flaw in the Playground chat interface of IBM Langflow OSS. Unsanitized Markdown rendering allows an attacker to inject malicious JavaScript that is persisted in the system and served to any user who views the affected chat. This can result in the theft of browser cookies, session hijacking, defacement, or arbitrary code execution within the victim’s browser context.

IBM Langflow OSS versions 1.0.0 through 1.11.2 are affected. These releases receive the flaw until the 1.11.3 release which includes the fix.

The CVSS score of 6.1 indicates moderate severity. Exploit probability is not available, and the flaw has not been listed in CISA’s KEV catalog. The likely attack path involves an attacker submitting malicious Markdown content to the Playground chat, which is then stored and later rendered to other users. The absence of a dedicated proxy header configuration suggests IP spoofing risks, but the primary exploitation vector is the chat interface.