diff --git a/lib/adapters/http.js b/lib/adapters/http.js
index 943bc429..63947ff4 100755
--- a/lib/adapters/http.js
+++ b/lib/adapters/http.js
@@ -520,7 +520,8 @@ export default isHttpAdapterSupported &&
           }
         );
         // support for https://www.npmjs.com/package/form-data api
-      } else if (utils.isFormData(data) && utils.isFunction(data.getHeaders)) {
+      } else if (utils.isFormData(data) && utils.isFunction(data.getHeaders) &&
+                 data.getHeaders !== Object.prototype.getHeaders) {
         headers.set(data.getHeaders());
 
         if (!headers.hasContentLength()) {
diff --git a/lib/utils.js b/lib/utils.js
index 73c4f0d2..6bcd6726 100644
--- a/lib/utils.js
+++ b/lib/utils.js
@@ -257,16 +257,16 @@ const G = getGlobal();
 const FormDataCtor = typeof G.FormData !== 'undefined' ? G.FormData : undefined;
 
 const isFormData = (thing) => {
-  let kind;
-  return thing && (
-    (FormDataCtor && thing instanceof FormDataCtor) || (
-      isFunction(thing.append) && (
-        (kind = kindOf(thing)) === 'formdata' ||
-        // detect form-data instance
-        (kind === 'object' && isFunction(thing.toString) && thing.toString() === '[object FormData]')
-      )
-    )
-  );
+  if (!thing) return false;
+  if (FormDataCtor && thing instanceof FormDataCtor) return true;
+  // Reject plain objects inheriting directly from Object.prototype so prototype-pollution gadgets can't spoof FormData (GHSA-6chq-wfr3-2hj9).
+  const proto = getPrototypeOf(thing);
+  if (!proto || proto === Object.prototype) return false;
+  if (!isFunction(thing.append)) return false;
+  const kind = kindOf(thing);
+  return kind === 'formdata' ||
+    // detect form-data instance
+    (kind === 'object' && isFunction(thing.toString) && thing.toString() === '[object FormData]');
 };
 
 /**
diff --git a/tests/unit/adapters/http.test.js b/tests/unit/adapters/http.test.js
index edf4d96f..3b492f29 100644
--- a/tests/unit/adapters/http.test.js
+++ b/tests/unit/adapters/http.test.js
@@ -2512,6 +2512,55 @@ describe('supports http with nodejs', () => {
         }
       });
     });
+
+    describe('prototype pollution (GHSA-6chq-wfr3-2hj9)', () => {
+      const pollutedKeys = ['getHeaders', 'append', 'pipe', 'on', 'once'];
+      const toStringTagSym = Symbol.toStringTag;
+
+      function pollute() {
+        Object.prototype[toStringTagSym] = 'FormData';
+        Object.prototype.append = () => {};
+        Object.prototype.getHeaders = () => ({
+          'x-injected': 'attacker',
+          'authorization': 'Bearer ATTACKER_TOKEN',
+        });
+        Object.prototype.pipe = function (d) { if (d && d.end) d.end(); return d; };
+        Object.prototype.on = function () { return this; };
+        Object.prototype.once = function () { return this; };
+      }
+
+      function cleanup() {
+        for (const k of pollutedKeys) delete Object.prototype[k];
+        delete Object.prototype[toStringTagSym];
+      }
+
+      it('should not merge prototype-polluted getHeaders into outgoing request', async () => {
+        let receivedHeaders;
+        const server = await startHTTPServer(
+          (req, res) => {
+            receivedHeaders = req.headers;
+            res.end('{}');
+          },
+          { port: SERVER_PORT }
+        );
+
+        try {
+          pollute();
+          await axios.post(
+            `http://localhost:${server.address().port}/`,
+            { userId: 42 },
+            { headers: { 'Authorization': 'Bearer VALID_USER_TOKEN' } }
+          );
+        } finally {
+          cleanup();
+          await stopHTTPServer(server);
+        }
+
+        assert.ok(receivedHeaders, 'request did not reach server');
+        assert.strictEqual(receivedHeaders['x-injected'], undefined);
+        assert.notStrictEqual(receivedHeaders['authorization'], 'Bearer ATTACKER_TOKEN');
+      });
+    });
   });
 
   describe('toFormData helper', () => {