render.execute_js

Execute JavaScript code on webpages to analyze client-side behavior, test for vulnerabilities, and automate security assessments during bug bounty hunting.

Instructions

Execute JavaScript in the context of a webpage

Input Schema

TableJSON Schema

Name	Required	Description	Default
`url`	Yes	URL to load
`script`	Yes	JavaScript code to execute

Implementation Reference

src/tools/render.ts:209-234 (handler)

The handler function for 'render.execute_js'. It creates a new browser page, navigates to the given URL, executes the provided JavaScript using page.evaluate with eval, and returns the result or error.

async ({ url, script }: any): Promise<ToolResult> => {
  let page: Page | null = null;
  try {
    const browserInstance = await getBrowser();
    page = await browserInstance.newPage();
    
    await page.goto(url, { waitUntil: 'networkidle2', timeout: 30000 });

    const result = await page.evaluate((scriptToRun) => {
      try {
        return eval(scriptToRun);
      } catch (e) {
        return { error: e instanceof Error ? e.message : String(e) };
      }
    }, script);

    await page.close();

    return formatToolResult(true, {
      url,
      result,
    });
  } catch (error: any) {
    if (page) await page.close().catch(() => {});
    return formatToolResult(false, null, error.message);
  }

src/tools/render.ts:200-207 (schema)

Input schema defining the parameters 'url' and 'script' for the 'render.execute_js' tool.

inputSchema: {
  type: 'object',
  properties: {
    url: { type: 'string', description: 'URL to load' },
    script: { type: 'string', description: 'JavaScript code to execute' },
  },
  required: ['url', 'script'],
},

src/tools/render.ts:196-236 (registration)

Registration of the 'render.execute_js' tool using server.tool() within the registerRenderTools function.

server.tool(
  'render.execute_js',
  {
    description: 'Execute JavaScript in the context of a webpage',
    inputSchema: {
      type: 'object',
      properties: {
        url: { type: 'string', description: 'URL to load' },
        script: { type: 'string', description: 'JavaScript code to execute' },
      },
      required: ['url', 'script'],
    },
  },
  async ({ url, script }: any): Promise<ToolResult> => {
    let page: Page | null = null;
    try {
      const browserInstance = await getBrowser();
      page = await browserInstance.newPage();
      
      await page.goto(url, { waitUntil: 'networkidle2', timeout: 30000 });

      const result = await page.evaluate((scriptToRun) => {
        try {
          return eval(scriptToRun);
        } catch (e) {
          return { error: e instanceof Error ? e.message : String(e) };
        }
      }, script);

      await page.close();

      return formatToolResult(true, {
        url,
        result,
      });
    } catch (error: any) {
      if (page) await page.close().catch(() => {});
      return formatToolResult(false, null, error.message);
    }
  }
);

src/index.ts:42-42 (registration)
Top-level call to registerRenderTools(server), which includes registration of 'render.execute_js'.
```
registerRenderTools(server);
```

src/tools/render.ts:9-17 (helper)

Helper function getBrowser() that provides a shared Puppeteer browser instance, used by the tool handler.

async function getBrowser(): Promise<Browser> {
  if (!browser) {
    browser = await puppeteer.launch({
      headless: true,
      args: ['--no-sandbox', '--disable-setuid-sandbox'],
    });
  }
  return browser;
}

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