fix(browser): cap click and key repeat counts in MCP (#1367)

* fix(browser): cap click and key repeat counts in MCP

* style: apply prettier formatting

lib/mcp/ccs-browser-server.cjs

@@ -159,6 +159,8 @@ const DEFAULT_WAIT_TIMEOUT_MS = 2000;
 const DEFAULT_WAIT_POLL_INTERVAL_MS = 100;
 const DEFAULT_DRAG_STEPS = 5;
 const MAX_POINTER_ACTIONS = 25;
+const MAX_CLICK_COUNT = 25;
+const MAX_KEY_REPEAT = 25;
 const SESSION_START_SETTLE_WINDOW_MS = 250;
 const MAX_ARTIFACT_FILE_BYTES = 5 * 1024 * 1024;
 const MAX_LOCAL_TRANSFER_FILE_BYTES = 10 * 1024 * 1024;
@@ -454,6 +456,7 @@ function getTools() {
           clickCount: {
             type: 'integer',
             minimum: 1,
+            maximum: MAX_CLICK_COUNT,
             description: 'Optional click count. Defaults to 1.',
           },
         },
@@ -519,6 +522,7 @@ function getTools() {
           repeat: {
             type: 'integer',
             minimum: 1,
+            maximum: MAX_KEY_REPEAT,
             description: 'Optional repeat count. Defaults to 1.',
           },
         },
@@ -2305,10 +2309,13 @@ function requirePositiveIntegerOrDefault(value, label, fallback) {
   return value;
 }
 
-function requirePositiveInteger(value, label) {
+function requirePositiveInteger(value, label, maximum = undefined) {
   if (!Number.isInteger(value) || value <= 0) {
     throw new Error(`${label} must be a positive integer`);
   }
+  if (maximum !== undefined && value > maximum) {
+    throw new Error(`${label} must be less than or equal to ${maximum}`);
+  }
   return value;
 }
 
@@ -3555,7 +3562,7 @@ async function handleClick(toolArgs) {
   const clickCount =
     toolArgs.clickCount === undefined
       ? 1
-      : requirePositiveInteger(toolArgs.clickCount, 'clickCount');
+      : requirePositiveInteger(toolArgs.clickCount, 'clickCount', MAX_CLICK_COUNT);
 
   const expression = `(() => {
     const selector = JSON.parse(${JSON.stringify(JSON.stringify(selector))});
@@ -3805,7 +3812,9 @@ async function handlePressKey(toolArgs) {
     'Shift',
   ]);
   const repeat =
-    toolArgs.repeat === undefined ? 1 : requirePositiveInteger(toolArgs.repeat, 'repeat');
+    toolArgs.repeat === undefined
+      ? 1
+      : requirePositiveInteger(toolArgs.repeat, 'repeat', MAX_KEY_REPEAT);
   const modifierMask =
     (modifiers.includes('Alt') ? 1 : 0) |
     (modifiers.includes('Control') ? 2 : 0) |

tests/unit/hooks/browser-mcp-navigation-and-query.test.ts

@@ -722,6 +722,47 @@ describe('ccs-browser MCP server - navigation and query', () => {
     );
   });
 
+
+  it('rejects excessive clickCount and repeat values', async () => {
+    const responses = await runMcpRequests(
+      [{ id: 'page-1', title: 'Limits Page', currentUrl: 'https://example.com/' }],
+      [
+        {
+          jsonrpc: '2.0',
+          id: 713,
+          method: 'tools/call',
+          params: {
+            name: 'browser_click',
+            arguments: {
+              selector: '#submit',
+              clickCount: 26,
+            },
+          },
+        },
+        {
+          jsonrpc: '2.0',
+          id: 714,
+          method: 'tools/call',
+          params: {
+            name: 'browser_press_key',
+            arguments: {
+              key: 'k',
+              repeat: 26,
+            },
+          },
+        },
+      ]
+    );
+
+    const clickResponse = responses.find((message) => message.id === 713);
+    expect((clickResponse?.result as { isError?: boolean }).isError).toBe(true);
+    expect(getResponseText(clickResponse)).toContain('clickCount must be less than or equal to 25');
+
+    const keyResponse = responses.find((message) => message.id === 714);
+    expect((keyResponse?.result as { isError?: boolean }).isError).toBe(true);
+    expect(getResponseText(keyResponse)).toContain('repeat must be less than or equal to 25');
+  });
+
   it('scrolls an element into view with browser_scroll', async () => {
     const responses = await runMcpRequests(
       [

tests/unit/hooks/browser-mcp-session-and-intercepts.test.ts

@@ -79,11 +79,17 @@ describe('ccs-browser MCP server - session and interception', () => {
     expect(clickTool?.inputSchema?.properties?.clickCount).toMatchObject({
       type: 'integer',
       minimum: 1,
+      maximum: 25,
     });
 
     const keyTool = tools.find((tool) => tool.name === 'browser_press_key');
     expect(keyTool?.inputSchema?.properties?.key).toMatchObject({ type: 'string' });
     expect(keyTool?.inputSchema?.properties?.modifiers).toMatchObject({ type: 'array' });
+    expect(keyTool?.inputSchema?.properties?.repeat).toMatchObject({
+      type: 'integer',
+      minimum: 1,
+      maximum: 25,
+    });
 
     const scrollTool = tools.find((tool) => tool.name === 'browser_scroll');
     expect(scrollTool?.inputSchema?.properties?.deltaX).toMatchObject({ type: 'number' });