diff --git a/action.yml b/action.yml
index 6a6792a3e..fa18b4ace 100644
--- a/action.yml
+++ b/action.yml
@@ -59,6 +59,9 @@ inputs:
   name:
     description: 'User defined upload name. Visible in Codecov UI'
     required: false
+  network_filter:
+    description: 'Used to restrict the set of git/hg files that can be matched with filenames in the coverage report. This is useful for monorepos or other setups where a full filepath may not be specified in the coverage report, and that shortened filepath may appear multiple times in a directory structure (e.g. __init__.py)'
+    required: false
   override_branch:
     description: 'Specify the branch name'
     required: false
@@ -74,9 +77,6 @@ inputs:
   override_tag:
     description: 'Specify the git tag'
     required: false
-  network_filter:
-    description: 'Used to restrict the set of git/hg files that can be matched with filenames in the coverage report. This is useful for monorepos or other setups where a full filepath may not be specified in the coverage report, and that shortened filepath may appear multiple times in a directory structure (e.g. __init__.py)'
-    required: false
   path_to_write_report:
     description: 'Write upload file to path before uploading'
     required: false
diff --git a/dist/index.js b/dist/index.js
index 707acd60f..ff84a32d3 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -13152,12 +13152,49 @@ module.exports = {"$id":"log.json#","$schema":"http://json-schema.org/draft-06/s
 
 "use strict";
 
+var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
+    return new (P || (P = Promise))(function (resolve, reject) {
+        function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
+        function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
+        step((generator = generator.apply(thisArg, _arguments || [])).next());
+    });
+};
+var __generator = (this && this.__generator) || function (thisArg, body) {
+    var _ = { label: 0, sent: function() { if (t[0] & 1) throw t[1]; return t[1]; }, trys: [], ops: [] }, f, y, t, g;
+    return g = { next: verb(0), "throw": verb(1), "return": verb(2) }, typeof Symbol === "function" && (g[Symbol.iterator] = function() { return this; }), g;
+    function verb(n) { return function (v) { return step([n, v]); }; }
+    function step(op) {
+        if (f) throw new TypeError("Generator is already executing.");
+        while (_) try {
+            if (f = 1, y && (t = op[0] & 2 ? y["return"] : op[0] ? y["throw"] || ((t = y["return"]) && t.call(y), 0) : y.next) && !(t = t.call(y, op[1])).done) return t;
+            if (y = 0, t) op = [op[0] & 2, t.value];
+            switch (op[0]) {
+                case 0: case 1: t = op; break;
+                case 4: _.label++; return { value: op[1], done: false };
+                case 5: _.label++; y = op[1]; op = [0]; continue;
+                case 7: op = _.ops.pop(); _.trys.pop(); continue;
+                default:
+                    if (!(t = _.trys, t = t.length > 0 && t[t.length - 1]) && (op[0] === 6 || op[0] === 2)) { _ = 0; continue; }
+                    if (op[0] === 3 && (!t || (op[1] > t[0] && op[1] < t[3]))) { _.label = op[1]; break; }
+                    if (op[0] === 6 && _.label < t[1]) { _.label = t[1]; t = op; break; }
+                    if (t && _.label < t[2]) { _.label = t[2]; _.ops.push(op); break; }
+                    if (t[2]) _.ops.pop();
+                    _.trys.pop(); continue;
+            }
+            op = body.call(thisArg, _);
+        } catch (e) { op = [6, e]; y = 0; } finally { f = t = 0; }
+        if (op[0] & 5) throw op[1]; return { value: op[0] ? op[1] : void 0, done: true };
+    }
+};
 exports.__esModule = true;
 var core = __webpack_require__(470);
 var exec = __webpack_require__(986);
 var fs = __webpack_require__(747);
 var request = __webpack_require__(335);
 var buildExec_1 = __webpack_require__(983);
+var validate_1 = __webpack_require__(743);
 var failCi;
 try {
     request({
@@ -13165,49 +13202,69 @@ try {
         maxAttempts: 10,
         timeout: 3000,
         url: 'https://codecov.io/bash',
-    }, function (error, response, body) {
-        var _a = buildExec_1["default"](), execArgs = _a.execArgs, options = _a.options, filepath = _a.filepath, failCi = _a.failCi;
-        try {
-            if (error && failCi) {
-                throw error;
-            }
-            else if (error) {
-                core.warning("Codecov warning: " + error.message);
-            }
-            fs.writeFile(filepath, body, function (err) {
-                if (err && failCi) {
-                    throw err;
-                }
-                else if (err) {
-                    core.warning("Codecov warning: " + err.message);
-                }
-                exec.exec('bash', execArgs, options)["catch"](function (err) {
-                    if (failCi) {
-                        core.setFailed("Codecov failed with the following error: " + err.message);
+    }, function (error, response, body) { return __awaiter(void 0, void 0, void 0, function () {
+        var _a, execArgs, options, filepath, failCi, isValid, failure, error_1;
+        return __generator(this, function (_b) {
+            switch (_b.label) {
+                case 0:
+                    _a = buildExec_1["default"](), execArgs = _a.execArgs, options = _a.options, filepath = _a.filepath, failCi = _a.failCi;
+                    _b.label = 1;
+                case 1:
+                    _b.trys.push([1, 3, , 4]);
+                    return [4 /*yield*/, validate_1["default"](body)];
+                case 2:
+                    isValid = _b.sent();
+                    if (!isValid) {
+                        failure = 'Codecov failure: ' +
+                            'Bash script checksums do not match published values. ' +
+                            'Please contact security@codecov.io immediately.';
+                        core.setFailed(failure);
+                        throw new Error(failure);
                     }
-                    else {
-                        core.warning("Codecov warning: " + err.message);
+                    if (error && failCi) {
+                        throw error;
                     }
-                })
-                    .then(function () {
-                    unlinkFile();
-                });
-                var unlinkFile = function () {
-                    fs.unlink(filepath, function (err) {
+                    else if (error) {
+                        core.warning("Codecov warning: " + error.message);
+                    }
+                    fs.writeFile(filepath, body, function (err) {
                         if (err && failCi) {
                             throw err;
                         }
                         else if (err) {
                             core.warning("Codecov warning: " + err.message);
                         }
+                        exec.exec('bash', execArgs, options)["catch"](function (err) {
+                            if (failCi) {
+                                core.setFailed("Codecov failed with the following error: " + err.message);
+                            }
+                            else {
+                                core.warning("Codecov warning: " + err.message);
+                            }
+                        })
+                            .then(function () {
+                            unlinkFile();
+                        });
+                        var unlinkFile = function () {
+                            fs.unlink(filepath, function (err) {
+                                if (err && failCi) {
+                                    throw err;
+                                }
+                                else if (err) {
+                                    core.warning("Codecov warning: " + err.message);
+                                }
+                            });
+                        };
                     });
-                };
-            });
-        }
-        catch (error) {
-            core.setFailed("Codecov failed with the following error: " + error.message);
-        }
-    });
+                    return [3 /*break*/, 4];
+                case 3:
+                    error_1 = _b.sent();
+                    core.setFailed("Codecov failed with the following error: " + error_1.message);
+                    return [3 /*break*/, 4];
+                case 4: return [2 /*return*/];
+            }
+        });
+    }); });
 }
 catch (error) {
     if (failCi) {
@@ -49116,7 +49173,121 @@ module.exports = function (data, opts) {
 
 
 /***/ }),
-/* 743 */,
+/* 743 */
+/***/ (function(__unusedmodule, exports, __webpack_require__) {
+
+"use strict";
+
+var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
+    return new (P || (P = Promise))(function (resolve, reject) {
+        function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
+        function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
+        step((generator = generator.apply(thisArg, _arguments || [])).next());
+    });
+};
+var __generator = (this && this.__generator) || function (thisArg, body) {
+    var _ = { label: 0, sent: function() { if (t[0] & 1) throw t[1]; return t[1]; }, trys: [], ops: [] }, f, y, t, g;
+    return g = { next: verb(0), "throw": verb(1), "return": verb(2) }, typeof Symbol === "function" && (g[Symbol.iterator] = function() { return this; }), g;
+    function verb(n) { return function (v) { return step([n, v]); }; }
+    function step(op) {
+        if (f) throw new TypeError("Generator is already executing.");
+        while (_) try {
+            if (f = 1, y && (t = op[0] & 2 ? y["return"] : op[0] ? y["throw"] || ((t = y["return"]) && t.call(y), 0) : y.next) && !(t = t.call(y, op[1])).done) return t;
+            if (y = 0, t) op = [op[0] & 2, t.value];
+            switch (op[0]) {
+                case 0: case 1: t = op; break;
+                case 4: _.label++; return { value: op[1], done: false };
+                case 5: _.label++; y = op[1]; op = [0]; continue;
+                case 7: op = _.ops.pop(); _.trys.pop(); continue;
+                default:
+                    if (!(t = _.trys, t = t.length > 0 && t[t.length - 1]) && (op[0] === 6 || op[0] === 2)) { _ = 0; continue; }
+                    if (op[0] === 3 && (!t || (op[1] > t[0] && op[1] < t[3]))) { _.label = op[1]; break; }
+                    if (op[0] === 6 && _.label < t[1]) { _.label = t[1]; t = op; break; }
+                    if (t && _.label < t[2]) { _.label = t[2]; _.ops.push(op); break; }
+                    if (t[2]) _.ops.pop();
+                    _.trys.pop(); continue;
+            }
+            op = body.call(thisArg, _);
+        } catch (e) { op = [6, e]; y = 0; } finally { f = t = 0; }
+        if (op[0] & 5) throw op[1]; return { value: op[0] ? op[1] : void 0, done: true };
+    }
+};
+exports.__esModule = true;
+exports.retrieveChecksum = void 0;
+var crypto = __webpack_require__(417);
+var core = __webpack_require__(470);
+var request = __webpack_require__(335);
+var validateUploader = function (body) { return __awaiter(void 0, void 0, void 0, function () {
+    var version, _i, _a, i, publicChecksum, uploaderChecksum;
+    return __generator(this, function (_b) {
+        switch (_b.label) {
+            case 0:
+                version = getVersion(body);
+                if (version === null) {
+                    core.warning('Codecov could not identify the bash uploader version.');
+                    return [2 /*return*/, false];
+                }
+                _i = 0, _a = [1, 256, 512];
+                _b.label = 1;
+            case 1:
+                if (!(_i < _a.length)) return [3 /*break*/, 4];
+                i = _a[_i];
+                return [4 /*yield*/, exports.retrieveChecksum(version, i)];
+            case 2:
+                publicChecksum = _b.sent();
+                uploaderChecksum = calculateChecksum(body, i);
+                if (uploaderChecksum !== publicChecksum.trim()) {
+                    core.warning("Codecov " + version + " checksums for SHA" + i + " failed to match.\n" +
+                        ("Public checksum:   " + publicChecksum) +
+                        ("Uploader checksum: " + uploaderChecksum));
+                    return [2 /*return*/, false];
+                }
+                _b.label = 3;
+            case 3:
+                _i++;
+                return [3 /*break*/, 1];
+            case 4: return [2 /*return*/, true];
+        }
+    });
+}); };
+var retrieveChecksum = function (version, encryption) { return __awaiter(void 0, void 0, void 0, function () {
+    var url, response;
+    return __generator(this, function (_a) {
+        switch (_a.label) {
+            case 0:
+                url = "https://raw.githubusercontent.com/codecov/codecov-bash/" + version + "/SHA" + encryption + "SUM";
+                return [4 /*yield*/, request({
+                        maxAttempts: 10,
+                        timeout: 3000,
+                        url: url,
+                    })];
+            case 1:
+                response = _a.sent();
+                if (response.statusCode != 200) {
+                    core.warning("Codecov could not retrieve checksum SHA" + encryption + " at " + url);
+                    return [2 /*return*/, ''];
+                }
+                return [2 /*return*/, response.body];
+        }
+    });
+}); };
+exports.retrieveChecksum = retrieveChecksum;
+var calculateChecksum = function (body, i) {
+    var shasum = crypto.createHash("sha" + i);
+    shasum.update(body);
+    return shasum.digest('hex') + "  codecov";
+};
+var getVersion = function (body) {
+    var regex = /VERSION="(.*)+"/g;
+    var match = regex.exec(body);
+    return match ? match[1] : null;
+};
+exports["default"] = validateUploader;
+
+
+/***/ }),
 /* 744 */
 /***/ (function(module) {
 
diff --git a/src/index.ts b/src/index.ts
index 12e294403..4cb77680c 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -5,6 +5,7 @@ const fs = require('fs');
 const request = require('requestretry');
 
 import buildExec from './buildExec';
+import validateUploader from './validate';
 
 let failCi;
 try {
@@ -13,10 +14,19 @@ try {
     maxAttempts: 10,
     timeout: 3000,
     url: 'https://codecov.io/bash',
-  }, (error, response, body) => {
+  }, async (error, response, body) => {
     const {execArgs, options, filepath, failCi} = buildExec();
 
     try {
+      const isValid = await validateUploader(body);
+      if (!isValid) {
+        const failure = 'Codecov failure: ' +
+            'Bash script checksums do not match published values. ' +
+            'Please contact security@codecov.io immediately.';
+        core.setFailed(failure);
+        throw new Error(failure);
+      }
+
       if (error && failCi) {
         throw error;
       } else if (error) {
diff --git a/src/validate.test.ts b/src/validate.test.ts
new file mode 100644
index 000000000..f59c8384c
--- /dev/null
+++ b/src/validate.test.ts
@@ -0,0 +1,39 @@
+import validateUploader, {retrieveChecksum} from './validate';
+
+const request = require('requestretry');
+
+const bashScript = (async () => {
+  try {
+    const script = await request({
+      json: false,
+      maxAttempts: 10,
+      timeout: 3000,
+      url: 'https://codecov.io/bash',
+    });
+    return script.body;
+  } catch (err) {
+    throw err;
+  }
+});
+
+test('valid checksums', async () => {
+  const valid = await validateUploader(await bashScript());
+  expect(valid).toBeTruthy();
+});
+
+test('invalid checksums', async () => {
+  const script = await bashScript();
+  const valid = await validateUploader(script.substring(0, script.length - 1));
+  expect(valid).toBeFalsy();
+});
+
+test('invalid script version', async () => {
+  const script = await bashScript();
+  const valid = await validateUploader(script.substring(0, 20));
+  expect(valid).toBeFalsy();
+});
+
+test('invalid public checksum file', async () => {
+  const checksum = await retrieveChecksum('foo', 'bar');
+  expect(checksum).toBeFalsy();
+});
diff --git a/src/validate.ts b/src/validate.ts
new file mode 100644
index 000000000..68cbd63ad
--- /dev/null
+++ b/src/validate.ts
@@ -0,0 +1,58 @@
+const crypto = require('crypto');
+
+const core = require('@actions/core');
+
+const request = require('requestretry');
+
+const validateUploader = async (body) => {
+  const version = getVersion(body);
+  if (version === null) {
+    core.warning('Codecov could not identify the bash uploader version.');
+    return false;
+  }
+
+  for (const i of [1, 256, 512]) {
+    const publicChecksum = await retrieveChecksum(version, i);
+    const uploaderChecksum = calculateChecksum(body, i);
+    if (uploaderChecksum !== publicChecksum.trim()) {
+      core.warning(
+          `Codecov ${version} checksums for SHA${i} failed to match.\n` +
+          `Public checksum:   ${publicChecksum}` +
+          `Uploader checksum: ${uploaderChecksum}`,
+      );
+      return false;
+    }
+  }
+  return true;
+};
+
+export const retrieveChecksum = async (version, encryption) => {
+  const url = `https://raw.githubusercontent.com/codecov/codecov-bash/${version}/SHA${encryption}SUM`;
+  const response = await request({
+    maxAttempts: 10,
+    timeout: 3000,
+    url: url,
+  });
+
+  if (response.statusCode != 200) {
+    core.warning(
+        `Codecov could not retrieve checksum SHA${encryption} at ${url}`,
+    );
+    return '';
+  }
+  return response.body;
+};
+
+const calculateChecksum = (body, i) => {
+  const shasum = crypto.createHash(`sha${i}`);
+  shasum.update(body);
+  return `${shasum.digest('hex')}  codecov`;
+};
+
+const getVersion = (body) => {
+  const regex = /VERSION="(.*)+"/g;
+  const match = regex.exec(body);
+  return match ? match[1] : null;
+};
+
+export default validateUploader;