Synopsis
Flowise uses the Flowise Chat Embed JavaScript library to display Flowise chatbot on a website. Flowise Chat Embed versions prior 2.0.0 suffer from a lack of sanitization of user inputs, allowing a remote and unauthenticated user to inject malicious JavaScript and perform Stored Cross-Site scripting attacks against the vulnerable instance.
Proof-of-Concept
Flowise's core features include the creation of chatflow, which could be translated as the creation of a chatbot that can then be embedded in a website.
When creating a flow, by starting a conversation with the bot we observed that certain HTML attributes are filtered, such as on* events.
It is however possible to use an XSS payload without an event handler, such as :
<iframe src=javascript:console.log(document.domain)>
As the chatbot is designed to be embedded on a website, the payload will then flow to the Flowise administration panel and being executed, allowing a random user starting a conversation with the chatbot to achieve the attack :
Solution
Upgrade to Flowise 2.1.1 or later. If using Flowise Chat Embed library only, upgrade to version 2.0.0 or later.
Additional References
https://github.com/FlowiseAI/Flowise/releases/tag/flowise%402.1.1https://github.com/FlowiseAI/FlowiseChatEmbed/releases/tag/flowise-embed%402.0.0
Disclosure Timeline
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