diff --git a/lib/deap.js b/lib/deap.js
index 6ac55f0..89ef559 100755
--- a/lib/deap.js
+++ b/lib/deap.js
@@ -12,6 +12,10 @@ module.exports = {
 	mergeShallow: merge
 };
 
+function getProp(obj, p) {
+	return p === '__proto__' ? undefined : obj[p];
+}
+
 function clone(val) {
 	switch(typeOf(val)) {
 		case 'object':
@@ -54,7 +58,7 @@ function extend(a, b /*, [b2..n] */) {
 function deepExtend(a, b /*, [b2..n] */) {
 	slice.call(arguments, 1).forEach(function(b) {
 		Object.keys(b).forEach(function(p) {
-			if(typeOf(b[p]) === 'object' && typeOf(a[p]) === 'object')
+			if(typeOf(getProp(b, p)) === 'object' && typeOf(a[p]) === 'object')
 				deepExtend(a[p], b[p]);
 			else
 				a[p] = deepClone(b[p]);
@@ -108,7 +112,7 @@ function deepMerge(a, b /*, [b2..n] */) {
 		var ap, bp, ta, tb;
 		Object.keys(b).forEach(function(p) {
 			ap = a[p];
-			bp = b[p];
+			bp = getProp(b, p);
 			ta = typeOf(ap);
 			tb = typeOf(bp);
 			if(tb === 'object' && ta === 'object')
diff --git a/test/extend.test.js b/test/extend.test.js
index aeeb9de..292dfe3 100755
--- a/test/extend.test.js
+++ b/test/extend.test.js
@@ -152,4 +152,15 @@ describe('deep extend', function() {
 		assert.notStrictEqual(result.nested[0].nested, result.nested[1]);
 	});
 
+	// Vulnerability reported via hacker1: https://hackerone.com/reports/310446
+	it('should not modify Object prototype (hacker1 #310446)', function() {
+		var a = { foo: 'bar' },
+			b = JSON.parse('{ "__proto__": { "evilBad": "DANGER!!!" } }');
+
+		var result = deepExtend(a, b);
+
+		assert.isUndefined({}.evilBad);
+		assert.isUndefined(Object.prototype.evilBad);
+	});
+
 });
diff --git a/test/merge.test.js b/test/merge.test.js
index 42fa2fa..94261f4 100644
--- a/test/merge.test.js
+++ b/test/merge.test.js
@@ -131,4 +131,14 @@ describe('deep merge', function() {
 		assert.notStrictEqual(result.nested[0], deeper);
 	});
 
+	// Vulnerability reported via hacker1: https://hackerone.com/reports/310446
+	it('should not modify Object prototype (hacker1 #310446)', function() {
+		var a = { foo: 'bar' },
+			b = JSON.parse('{ "__proto__": { "evilBad": "DANGER!!!" } }');
+
+		var result = deepMerge(a, b);
+
+		assert.isUndefined({}.evilBad);
+		assert.isUndefined(Object.prototype.evilBad);
+	});
 });