Cross-site Scripting (XSS) Affecting @n8n/n8n-nodes-langchain package, versions <1.122.19>=2.0.0-rc.0 <2.13.1<2.14.1

@n8n/n8n-nodes-langchain is a

Affected versions of this package are vulnerable to Cross-site Scripting (XSS) via the ChatTrigger template rendering in ChatTrigger/templates.ts. An authenticated user who can create or edit workflows can inject malicious JavaScript by supplying crafted Custom CSS in a Chat Trigger node, and anyone visiting the public chat page will execute it. The flaw allows the attacker to persist a script in the workflow configuration and have it run in other users’ browsers at the chat URL, exposing session data or enabling actions in the victim’s browser under their identity.

Notes

• The vulnerable flow is the HTML template used by the public chat page, so the stored payload runs wherever that chat URL is rendered rather than only inside the workflow editor.
• The issue is gated by workflow edit/create permissions: only users who can modify workflows can place the malicious Custom CSS into the Chat Trigger node.

Workarounds

• Limit workflow creation and editing permissions to fully trusted users only, which reduces the chance that an untrusted authenticated user can store malicious Custom CSS in a Chat Trigger workflow.
• Disable the Chat Trigger node by adding @n8n/n8n-nodes-langchain.chatTrigger to the NODES_EXCLUDE environment variable, which prevents the vulnerable public chat page from being exposed.

Cross-site scripting (or XSS) is a code vulnerability that occurs when an attacker “injects” a malicious script into an otherwise trusted website. The injected script gets downloaded and executed by the end user’s browser when the user interacts with the compromised website.

This is done by escaping the context of the web application; the web application then delivers that data to its users along with other trusted dynamic content, without validating it. The browser unknowingly executes malicious script on the client side (through client-side languages; usually JavaScript or HTML) in order to perform actions that are otherwise typically blocked by the browser’s Same Origin Policy.

Injecting malicious code is the most prevalent manner by which XSS is exploited; for this reason, escaping characters in order to prevent this manipulation is the top method for securing code against this vulnerability.

Escaping means that the application is coded to mark key characters, and particularly key characters included in user input, to prevent those characters from being interpreted in a dangerous context. For example, in HTML, < can be coded as &lt; and > can be coded as &gt; in order to be interpreted and displayed as themselves in text, while within the code itself, they are used for HTML tags. If malicious content is injected into an application that escapes special characters and that malicious content uses < and > as HTML tags, those characters are nonetheless not interpreted as HTML tags by the browser if they’ve been correctly escaped in the application code and in this way the attempted attack is diverted.

The most prominent use of XSS is to steal cookies (source: OWASP HttpOnly) and hijack user sessions, but XSS exploits have been used to expose sensitive information, enable access to privileged services and functionality and deliver malware.

Types of attacks

There are a few methods by which XSS can be manipulated:

Type	Origin	Description
Stored	Server	The malicious code is inserted in the application (usually as a link) by the attacker. The code is activated every time a user clicks the link.
Reflected	Server	The attacker delivers a malicious link externally from the vulnerable web site application to a user. When clicked, malicious code is sent to the vulnerable web site, which reflects the attack back to the user’s browser.
DOM-based	Client	The attacker forces the user’s browser to render a malicious page. The data in the page itself delivers the cross-site scripting data.
Mutated		The attacker injects code that appears safe, but is then rewritten and modified by the browser, while parsing the markup. An example is rebalancing unclosed quotation marks or even adding quotation marks to unquoted parameters.

Affected environments

The following environments are susceptible to an XSS attack:

• Web servers
• Application servers
• Web application environments

How to prevent

This section describes the top best practices designed to specifically protect your code:

• Sanitize data input in an HTTP request before reflecting it back, ensuring all data is validated, filtered or escaped before echoing anything back to the user, such as the values of query parameters during searches.
• Convert special characters such as ?, &, /, <, > and spaces to their respective HTML or URL encoded equivalents.
• Give users the option to disable client-side scripts.
• Redirect invalid requests.
• Detect simultaneous logins, including those from two separate IP addresses, and invalidate those sessions.
• Use and enforce a Content Security Policy (source: Wikipedia) to disable any features that might be manipulated for an XSS attack.
• Read the documentation for any of the libraries referenced in your code to understand which elements allow for embedded HTML.

• GitHub Commit n8n@1.123.27
• GitHub Commit n8n@2.13.3
• GitHub Commit n8n@2.14.1
• Maintainer's Advisory