diff --git a/src/Symfony/Component/Validator/Constraints/NotPwned.php b/src/Symfony/Component/Validator/Constraints/NotPwned.php
new file mode 100644
index 0000000000..9872076b73
--- /dev/null
+++ b/src/Symfony/Component/Validator/Constraints/NotPwned.php
@@ -0,0 +1,33 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Validator\Constraints;
+
+use Symfony\Component\Validator\Constraint;
+
+/**
+ * Checks if a password has been leaked in a data breach.
+ *
+ * @Annotation
+ * @Target({"PROPERTY", "METHOD", "ANNOTATION"})
+ *
+ * @author Kévin Dunglas <dunglas@gmail.com>
+ */
+class NotPwned extends Constraint
+{
+    const PWNED_ERROR = 'd9bcdbfe-a9d6-4bfa-a8ff-da5fd93e0f6d';
+
+    protected static $errorNames = [self::PWNED_ERROR => 'PWNED_ERROR'];
+
+    public $message = 'This password has been leaked in a data breach, it must not be used. Please use another password.';
+    public $threshold = 1;
+    public $skipOnError = false;
+}
diff --git a/src/Symfony/Component/Validator/Constraints/NotPwnedValidator.php b/src/Symfony/Component/Validator/Constraints/NotPwnedValidator.php
new file mode 100644
index 0000000000..d0beffb4f2
--- /dev/null
+++ b/src/Symfony/Component/Validator/Constraints/NotPwnedValidator.php
@@ -0,0 +1,90 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Validator\Constraints;
+
+use Symfony\Component\HttpClient\HttpClient;
+use Symfony\Component\Validator\Constraint;
+use Symfony\Component\Validator\ConstraintValidator;
+use Symfony\Component\Validator\Exception\UnexpectedTypeException;
+use Symfony\Contracts\HttpClient\Exception\ExceptionInterface;
+use Symfony\Contracts\HttpClient\HttpClientInterface;
+
+/**
+ * Checks if a password has been leaked in a data breach using haveibeenpwned.com's API.
+ * Use a k-anonymity model to protect the password being searched for.
+ *
+ * @see https://haveibeenpwned.com/API/v2#SearchingPwnedPasswordsByRange
+ *
+ * @author Kévin Dunglas <dunglas@gmail.com>
+ */
+class NotPwnedValidator extends ConstraintValidator
+{
+    private const RANGE_API = 'https://api.pwnedpasswords.com/range/%s';
+
+    private $httpClient;
+
+    public function __construct(HttpClientInterface $httpClient = null)
+    {
+        if (null === $httpClient && !class_exists(HttpClient::class)) {
+            throw new \LogicException(sprintf('The "%s" class requires the "HttpClient" component. Try running "composer require symfony/http-client".', self::class));
+        }
+
+        $this->httpClient = $httpClient ?? HttpClient::create();
+    }
+
+    /**
+     * {@inheritdoc}
+     *
+     * @throws ExceptionInterface
+     */
+    public function validate($value, Constraint $constraint)
+    {
+        if (!$constraint instanceof NotPwned) {
+            throw new UnexpectedTypeException($constraint, NotPwned::class);
+        }
+
+        if (null !== $value && !is_scalar($value) && !(\is_object($value) && method_exists($value, '__toString'))) {
+            throw new UnexpectedTypeException($value, 'string');
+        }
+
+        $value = (string) $value;
+        if ('' === $value) {
+            return;
+        }
+
+        $hash = strtoupper(sha1($value));
+        $hashPrefix = substr($hash, 0, 5);
+        $url = sprintf(self::RANGE_API, $hashPrefix);
+
+        try {
+            $result = $this->httpClient->request('GET', $url)->getContent();
+        } catch (ExceptionInterface $e) {
+            if ($constraint->skipOnError) {
+                return;
+            }
+
+            throw $e;
+        }
+
+        foreach (explode("\r\n", $result) as $line) {
+            list($hashSuffix, $count) = explode(':', $line);
+
+            if ($hashPrefix.$hashSuffix === $hash && $constraint->threshold <= (int) $count) {
+                $this->context->buildViolation($constraint->message)
+                    ->setCode(NotPwned::PWNED_ERROR)
+                    ->addViolation();
+
+                return;
+            }
+        }
+    }
+}
diff --git a/src/Symfony/Component/Validator/Tests/Constraints/NotPwnedTest.php b/src/Symfony/Component/Validator/Tests/Constraints/NotPwnedTest.php
new file mode 100644
index 0000000000..7d312d8281
--- /dev/null
+++ b/src/Symfony/Component/Validator/Tests/Constraints/NotPwnedTest.php
@@ -0,0 +1,28 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Validator\Tests\Constraints;
+
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\Validator\Constraints\NotPwned;
+
+/**
+ * @author Kévin Dunglas <dunglas@gmail.com>
+ */
+class NotPwnedTest extends TestCase
+{
+    public function testDefaultValues()
+    {
+        $constraint = new NotPwned();
+        $this->assertSame(1, $constraint->threshold);
+        $this->assertFalse($constraint->skipOnError);
+    }
+}
diff --git a/src/Symfony/Component/Validator/Tests/Constraints/NotPwnedValidatorTest.php b/src/Symfony/Component/Validator/Tests/Constraints/NotPwnedValidatorTest.php
new file mode 100644
index 0000000000..845ddbde39
--- /dev/null
+++ b/src/Symfony/Component/Validator/Tests/Constraints/NotPwnedValidatorTest.php
@@ -0,0 +1,145 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Validator\Tests\Constraints;
+
+use Symfony\Component\Validator\Constraints\Luhn;
+use Symfony\Component\Validator\Constraints\NotPwned;
+use Symfony\Component\Validator\Constraints\NotPwnedValidator;
+use Symfony\Component\Validator\Test\ConstraintValidatorTestCase;
+use Symfony\Contracts\HttpClient\Exception\ServerExceptionInterface;
+use Symfony\Contracts\HttpClient\HttpClientInterface;
+use Symfony\Contracts\HttpClient\ResponseInterface;
+
+/**
+ * @author Kévin Dunglas <dunglas@gmail.com>
+ */
+class NotPwnedValidatorTest extends ConstraintValidatorTestCase
+{
+    private const PASSWORD_TRIGGERING_AN_ERROR = 'apiError';
+    private const PASSWORD_TRIGGERING_AN_ERROR_RANGE_URL = 'https://api.pwnedpasswords.com/range/3EF27'; // https://api.pwnedpasswords.com/range/3EF27 is the range for the value "apiError"
+    private const PASSWORD_LEAKED = 'maman';
+    private const PASSWORD_NOT_LEAKED = ']<0585"%sb^5aa$w6!b38",,72?dp3r4\45b28Hy';
+
+    private const RETURN = [
+        '35E033023A46402F94CFB4F654C5BFE44A1:1',
+        '35F079CECCC31812288257CD770AA7968D7:53',
+        '36039744C253F9B2A4E90CBEDB02EBFB82D:5', // this is the matching line, password: maman
+        '3686792BBC66A72D40D928ED15621124CFE:7',
+        '36EEC709091B810AA240179A44317ED415C:2',
+    ];
+
+    protected function createValidator()
+    {
+        $httpClientStub = $this->createMock(HttpClientInterface::class);
+        $httpClientStub->method('request')->will(
+            $this->returnCallback(function (string $method, string $url): ResponseInterface {
+                if (self::PASSWORD_TRIGGERING_AN_ERROR_RANGE_URL === $url) {
+                    throw new class('Problem contacting the Have I been Pwned API.') extends \Exception implements ServerExceptionInterface {
+                        public function getResponse(): ResponseInterface
+                        {
+                            throw new \RuntimeException('Not implemented');
+                        }
+                    };
+                }
+
+                $responseStub = $this->createMock(ResponseInterface::class);
+                $responseStub
+                    ->method('getContent')
+                    ->willReturn(implode("\r\n", self::RETURN));
+
+                return $responseStub;
+            })
+        );
+
+        // Pass HttpClient::create() instead of this mock to run the tests against the real API
+        return new NotPwnedValidator($httpClientStub);
+    }
+
+    public function testNullIsValid()
+    {
+        $this->validator->validate(null, new NotPwned());
+
+        $this->assertNoViolation();
+    }
+
+    public function testEmptyStringIsValid()
+    {
+        $this->validator->validate('', new NotPwned());
+
+        $this->assertNoViolation();
+    }
+
+    public function testInvalidPassword()
+    {
+        $constraint = new NotPwned();
+        $this->validator->validate(self::PASSWORD_LEAKED, $constraint);
+
+        $this->buildViolation($constraint->message)
+            ->setCode(NotPwned::PWNED_ERROR)
+            ->assertRaised();
+    }
+
+    public function testThresholdReached()
+    {
+        $constraint = new NotPwned(['threshold' => 3]);
+        $this->validator->validate(self::PASSWORD_LEAKED, $constraint);
+
+        $this->buildViolation($constraint->message)
+            ->setCode(NotPwned::PWNED_ERROR)
+            ->assertRaised();
+    }
+
+    public function testThresholdNotReached()
+    {
+        $this->validator->validate(self::PASSWORD_LEAKED, new NotPwned(['threshold' => 10]));
+
+        $this->assertNoViolation();
+    }
+
+    public function testValidPassword()
+    {
+        $this->validator->validate(self::PASSWORD_NOT_LEAKED, new NotPwned());
+
+        $this->assertNoViolation();
+    }
+
+    /**
+     * @expectedException \Symfony\Component\Validator\Exception\UnexpectedTypeException
+     */
+    public function testInvalidConstraint()
+    {
+        $this->validator->validate(null, new Luhn());
+    }
+
+    /**
+     * @expectedException \Symfony\Component\Validator\Exception\UnexpectedTypeException
+     */
+    public function testInvalidValue()
+    {
+        $this->validator->validate([], new NotPwned());
+    }
+
+    /**
+     * @expectedException \Symfony\Contracts\HttpClient\Exception\ExceptionInterface
+     * @expectedExceptionMessage Problem contacting the Have I been Pwned API.
+     */
+    public function testApiError()
+    {
+        $this->validator->validate(self::PASSWORD_TRIGGERING_AN_ERROR, new NotPwned());
+    }
+
+    public function testApiErrorSkipped()
+    {
+        $this->validator->validate(self::PASSWORD_TRIGGERING_AN_ERROR, new NotPwned(['skipOnError' => true]));
+        $this->assertTrue(true); // No exception have been thrown
+    }
+}
diff --git a/src/Symfony/Component/Validator/composer.json b/src/Symfony/Component/Validator/composer.json
index c17fd098f5..8cba722fc1 100644
--- a/src/Symfony/Component/Validator/composer.json
+++ b/src/Symfony/Component/Validator/composer.json
@@ -22,6 +22,7 @@
         "symfony/polyfill-mbstring": "~1.0"
     },
     "require-dev": {
+        "symfony/http-client": "^4.3",
         "symfony/http-foundation": "~4.1",
         "symfony/http-kernel": "~3.4|~4.0",
         "symfony/var-dumper": "~3.4|~4.0",