diff --git a/src/Api/SecurityIssues.php b/src/Api/SecurityIssues.php
index a891483..0c2f05a 100644
--- a/src/Api/SecurityIssues.php
+++ b/src/Api/SecurityIssues.php
@@ -50,4 +50,19 @@ public function all(array $filters = [])
     {
         return $this->get('/security-issues/', $filters);
     }
+
+    public function show(int $issueId): array
+    {
+        return $this->get('/security-issues/' . $issueId);
+    }
+
+    public function open(int $issueId): array
+    {
+        return $this->post('/security-issues/' . $issueId . '/open');
+    }
+
+    public function close(int $issueId, string $state): array
+    {
+        return $this->post('/security-issues/' . $issueId . '/close/' . $state);
+    }
 }
diff --git a/tests/Api/SecurityIssuesTest.php b/tests/Api/SecurityIssuesTest.php
index 7b3979e..cdb6f02 100644
--- a/tests/Api/SecurityIssuesTest.php
+++ b/tests/Api/SecurityIssuesTest.php
@@ -13,7 +13,7 @@
 
 class SecurityIssuesTest extends ApiTestCase
 {
-    public function testAll()
+    public function testAll(): void
     {
         $expected = [
             [
@@ -41,7 +41,7 @@ public function testAll()
         $this->assertSame($expected, $api->all());
     }
 
-    public function testAllWithFilters()
+    public function testAllWithFilters(): void
     {
         $expected = [
             [
@@ -73,7 +73,85 @@ public function testAllWithFilters()
         $this->assertSame($expected, $api->all($filters));
     }
 
-    protected function getApiClass()
+    public function testShow(): void
+    {
+        $expected = [
+            'packageName' => 'acme-website/package',
+            'state' => 'open',
+            'branch' => 'dev-master',
+            'installedPackage' => 'acme/library',
+            'installedVersion' => '1.0.0',
+            'advisory' => [
+                'title' => 'CVE-1999: Remote code execution',
+                'link' =>'https://acme.website/security-advisories',
+                'cve' => 'CVE-1999',
+                'affectedVersions' => '>=1.0',
+            ],
+        ];
+
+        /** @var SecurityIssues&MockObject $api */
+        $api = $this->getApiMock();
+        $api->expects($this->once())
+            ->method('get')
+            ->with($this->equalTo('/security-issues/12'))
+            ->willReturn($expected);
+
+        $this->assertSame($expected, $api->show(12));
+    }
+
+    public function testOpen(): void
+    {
+        $expected = [
+            'packageName' => 'acme-website/package',
+            'state' => 'open',
+            'branch' => 'dev-master',
+            'installedPackage' => 'acme/library',
+            'installedVersion' => '1.0.0',
+            'advisory' => [
+                'title' => 'CVE-1999: Remote code execution',
+                'link' =>'https://acme.website/security-advisories',
+                'cve' => 'CVE-1999',
+                'affectedVersions' => '>=1.0',
+            ],
+        ];
+
+        /** @var SecurityIssues&MockObject $api */
+        $api = $this->getApiMock();
+        $api->expects($this->once())
+            ->method('post')
+            ->with($this->equalTo('/security-issues/12/open'))
+            ->willReturn($expected);
+
+        $this->assertSame($expected, $api->open(12));
+    }
+
+    public function testClose(): void
+    {
+        $expected = [
+            'packageName' => 'acme-website/package',
+            'state' => SecurityIssues::STATE_IN_PROGRESS,
+            'branch' => 'dev-master',
+            'installedPackage' => 'acme/library',
+            'installedVersion' => '1.0.0',
+            'advisory' => [
+                'title' => 'CVE-1999: Remote code execution',
+                'link' =>'https://acme.website/security-advisories',
+                'cve' => 'CVE-1999',
+                'affectedVersions' => '>=1.0',
+            ],
+        ];
+
+        /** @var SecurityIssues&MockObject $api */
+        $api = $this->getApiMock();
+        $api->expects($this->once())
+            ->method('post')
+            ->with($this->equalTo('/security-issues/12/close/' . SecurityIssues::STATE_IN_PROGRESS))
+            ->willReturn($expected);
+
+        $this->assertSame($expected, $api->close(12, SecurityIssues::STATE_IN_PROGRESS));
+    }
+
+    protected function getApiClass(): string
     {
         return SecurityIssues::class;
     }