Now also preventing the user of "Shared" as mountpoint

apps/files_external/lib/config.php

@@ -267,8 +267,8 @@ class OC_Mount_Config {
 										 $applicable,
 										 $isPersonal = false) {
 		$mountPoint = OC\Files\Filesystem::normalizePath($mountPoint);
-		if ($mountPoint === '' || $mountPoint === '/') {
-			// can't mount at root
+		if ($mountPoint === '' || $mountPoint === '/' || $mountPoint == '/Shared') {
+			// can't mount at root or "Shared" folder
 			return false;
 		}
 		if ($isPersonal) {

apps/files_external/tests/mountconfig.php

@@ -44,6 +44,8 @@ class Test_Mount_Config extends \PHPUnit_Framework_TestCase {
 		$isPersonal = false;
 		$this->assertEquals(false, OC_Mount_Config::addMountPoint('', $storageClass, array(), $mountType, $applicable, $isPersonal));
 		$this->assertEquals(false, OC_Mount_Config::addMountPoint('/', $storageClass, array(), $mountType, $applicable, $isPersonal));
+		$this->assertEquals(false, OC_Mount_Config::addMountPoint('Shared', $storageClass, array(), $mountType, $applicable, $isPersonal));
+		$this->assertEquals(false, OC_Mount_Config::addMountPoint('/Shared', $storageClass, array(), $mountType, $applicable, $isPersonal));
 
 	}
 }