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Handling Sensitive Data

When working with sensitive information like passwords or PII, you can use the Agent(sensitiveData=...) parameter to provide sensitive strings that the model can use in actions without ever seeing directly. 
const agent = new Agent(
    {
        task: "Log into example.com as user x_username with password x_password",
        llm: llm,
        sensitiveData: {
            "https://example.com": {
              "x_username": "abc@example.com",
              "x_password": "abc123456", // 'x_placeholder': '<actual secret value>',
            },
        },
    }
);
You should also configure BrowserSession(allowedDomains=...) to prevent the Agent from visiting URLs not needed for the task.

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Basic Usage

Here’s a basic example of how to use sensitive data: 
import { ChatOpenAI } from "browsernode/llm";
import { Agent, BrowserSession } from "browsernode";

const llm = new ChatOpenAI({ model: "gpt-4.1" });

// Define sensitive data
// The LLM will only see placeholder names (x_member_number, x_passphrase), never the actual values
const sensitiveData = {
    'https://*.example.com': {
        'x_member_number': '123235325',
        'x_passphrase': 'abcwe234',
    },
}

// Use the placeholder names in your task description
const task = `
1. go to https://travel.example.com
2. sign in with your member number x_member_number and private access code x_passphrase
3. extract today's list of travel deals as JSON
`;

// Recommended: Limit the domains available for the entire browser so the Agent can't be tricked into visiting untrusted URLs
const browserSession = new BrowserSession({ allowedDomains: ["https://*.example.com"] });

const agent = new Agent(
    {
        task: task,
        llm: llm,
        sensitiveData: sensitiveData, // Pass the sensitive data to the agent
        browserSession: browserSession, // Pass the restricted browserSession to limit URLs Agent can visit
        useVision: false, // Disable vision or else the LLM might see entered values in screenshots
    }
);

async function main() {
    await agent.run();
}

main().catch(console.error);
In this example:
  1. The LLM only ever sees the x_member_number and x_passphrase placeholders in prompts
  2. When the model wants to use your password it outputs x_passphrase - and we replace it with the actual value in the DOM
  3. When sensitive data appear in the content of the current page, we replace it in the page summary fed to the LLM - so that the model never has it in its state.
  4. The browser will be entirely prevented from going to any site not under https://*.example.com
This approach ensures that sensitive information remains secure while still allowing the agent to perform tasks that require authentication.

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Best Practices

  • Always restrict your sensitive data to only the exact domains that need it, https://travel.example.com is better than *.example.com
  • Always restrict BrowserSession(allowedDomains=[...]) to only the domains the agent needs to visit to accomplish its task. This helps guard against prompt injection attacks, jailbreaks, and LLM mistakes.
  • Only use sensitiveData for strings that can be inputted verbatim as text. The LLM never sees the actual values, so it can’t “understand” them, adapt them, or split them up for multiple input fields. For example, you can’t ask the Agent to click through a datepicker UI to input the sensitive value 1990-12-31. For these situations you can implement a custom function the LLM can call that updates the DOM using Python / JS.
  • Don’t use sensitiveData for login credentials, it’s better to use storageState or a userDataDir to log into the sites the agent needs in advance & reuse the cookies:
# open a browser to log into the sites you need & save the cookies
$ playwright open https://accounts.google.com --save-storage auth.json
Then use those cookies when the agent runs: 
const agent = new Agent(
    //...
    {
        browserSession: new BrowserSession({ storageState: "./auth.json" }),
    }
);
Warning: Vision models still see the screenshot of the page by default - where the sensitive data might be visible.It’s recommended to set Agent(useVision=false) when working with sensitiveData.

​
Allowed Domains

Domain patterns in sensitiveData follow the same format as allowedDomains:
  • example.com - Matches only https://example.com/*
  • *.example.com - Matches https://example.com/* and any subdomain https://*.example.com/*
  • http*://example.com - Matches both http:// and https:// protocols for example.com/*
  • chrome-extension://* - Matches any Chrome extension URL e.g. chrome-extension://anyextensionid/options.html
Security Warning: For security reasons, certain patterns are explicitly rejected:
  • Wildcards in TLD part (e.g., example.*) are not allowed (google.* would match google.ninja, google.pizza, etc. which is a bad idea)
  • Embedded wildcards (e.g., g*e.com) are rejected to prevent overly broad matches
  • Multiple wildcards like *.*.domain are not supported currently, open an issue if you need this feature
The default protocol when no scheme is specified is now https:// for enhanced security. For convenience the system will validate that all domain patterns used in Agent(sensitiveData) are also included in BrowserSession(allowedDomains).

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Missing or Empty Values

When working with sensitive data, keep these details in mind:
  • If a key referenced by the model (<secret>key_name</secret>) is missing from your sensitiveData dictionary, a warning will be logged but the substitution tag will be preserved.
  • If you provide an empty value for a key in the sensitiveData dictionary, it will be treated the same as a missing key.
  • The system will always attempt to process all valid substitutions, even if some keys are missing or empty.

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Full Example

Here’s a more complex example demonstrating multiple domains and sensitive data values. 
import { ChatOpenAI } from "browsernode/llm";
import { Agent, BrowserSession } from "browsernode";

const llm = new ChatOpenAI({ model: "gpt-4.1" });

// Domain-specific sensitive data
const sensitiveData = {
    'https://*.google.com': {'x_email': '...', 'x_pass': '...'},
    'chrome-extension://abcd1243': {'x_api_key': '...'},
    'http*://example.com': {'x_authcode': '123123'}
}

// Set browser session with allowed domains that match all domain patterns in sensitive_data
const browserSession = new BrowserSession({
    allowedDomains: [
        "https://*.google.com",
        "chrome-extension://abcd",
        "http://example.com", // Explicitly include http:// if needed
        "https://example.com", // By default, only https:// is matched
    ],
)

// Pass the sensitive data to the agent
const agent = new Agent(
    {
        task:"Log into Google, then check my account information",
        llm: llm,
        sensitiveData: sensitiveData,
        browserSession: browserSession,
        useVision: false,
    }
)

async function main() {
    await agent.run();
}

main().catch(console.error);
With this approach:
  1. The Google credentials (x_email and x_pass) will only be used on Google domains (any subdomain, https only)
  2. The API key (x_api_key) will only be used on pages served by the specific Chrome extension abcd1243
  3. The auth code (x_authcode) will only be used on http://example.com/* or https://example.com/*