diff --git a/cyr-to-lat.php b/cyr-to-lat.php
index 359fe6f..e331bee 100644
--- a/cyr-to-lat.php
+++ b/cyr-to-lat.php
@@ -10,7 +10,7 @@
  * Plugin Name:       Cyr-To-Lat
  * Plugin URI:        https://wordpress.org/plugins/cyr2lat/
  * Description:       Convert Non-Latin characters in post and term slugs to Latin characters. Useful for creating human-readable URLs. Based on the original plugin by Anton Skorobogatov.
- * Version:           5.2.2
+ * Version:           5.2.3
  * Requires at least: 5.1
  * Requires PHP:      5.6.20
  * Author:            Sergey Biryukov, Mikhail Kobzarev, Igor Gergel
@@ -36,7 +36,7 @@
 /**
  * Plugin version.
  */
-define( 'CYR_TO_LAT_VERSION', '5.2.2' );
+define( 'CYR_TO_LAT_VERSION', '5.2.3' );
 
 /**
  * Path to the plugin dir.
diff --git a/readme.txt b/readme.txt
index 097f916..194fb48 100644
--- a/readme.txt
+++ b/readme.txt
@@ -3,7 +3,7 @@ Contributors: SergeyBiryukov, mihdan, karevn, webvitaly, kaggdesign
 Tags: cyrillic, belorussian, ukrainian, bulgarian, macedonian, georgian, kazakh, latin, l10n, russian, cyr-to-lat, cyr2lat, rustolat, slugs, translations, transliteration
 Requires at least: 5.1
 Tested up to: 5.8
-Stable tag: 5.2.2
+Stable tag: 5.2.3
 Requires PHP: 5.6.20
 
 Convert Non-Latin characters in post, page and term slugs to Latin characters.
@@ -188,6 +188,10 @@ Yes you can!
 
 == Changelog ==
 
+= 5.2.3 (07.09.2021) =
+* Fix issue with WP Foro plugin - transliterate topic slug when created on frontend.
+* Fix bug with Polylang on REST request.
+
 = 5.2.2 (06.09.2021) =
 * Fix issue caused by the bug in Jetpack sync.
 * Optimize code related to WPML locale filtering.
diff --git a/src/php/class-main.php b/src/php/class-main.php
index 00820e5..db3a499 100644
--- a/src/php/class-main.php
+++ b/src/php/class-main.php
@@ -114,7 +114,7 @@ class Main {
 	public function __construct() {
 		$this->request = new Request();
 
-		if ( $this->request->is_frontend() ) {
+		if ( ! $this->request->is_allowed() ) {
 			return;
 		}
 
@@ -149,7 +149,7 @@ public function __construct() {
 	 * @noinspection PhpUndefinedClassInspection
 	 */
 	public function init() {
-		if ( $this->request->is_frontend() ) {
+		if ( ! $this->request->is_allowed() ) {
 			return;
 		}
 
@@ -533,7 +533,7 @@ public function pll_locale_filter( $locale ) {
 	 * @return false|null|string
 	 */
 	private function pll_locale_filter_with_rest() {
-		if ( ! $this->request->is_rest() ) {
+		if ( ! defined( 'REST_REQUEST' ) || ! constant( 'REST_REQUEST' ) ) {
 			return null;
 		}
 
diff --git a/src/php/class-request.php b/src/php/class-request.php
index af47113..4f83ff8 100644
--- a/src/php/class-request.php
+++ b/src/php/class-request.php
@@ -14,6 +14,15 @@
  */
 class Request {
 
+	/**
+	 * Is allowed request for plugin to work.
+	 *
+	 * @return bool
+	 */
+	public function is_allowed() {
+		return ! $this->is_frontend() || ( $this->is_frontend() && $this->is_post() );
+	}
+
 	/**
 	 * Is frontend.
 	 *
@@ -88,4 +97,18 @@ protected function get_rest_route() {
 
 		return $is_rest ? substr( $current_path, strlen( $rest_path ) ) : '';
 	}
+
+	/**
+	 * If current request is POST.
+	 *
+	 * @return bool
+	 */
+	public function is_post() {
+		$request_method = filter_var(
+			isset( $_SERVER['REQUEST_METHOD'] ) ? wp_unslash( $_SERVER['REQUEST_METHOD'] ) : '',
+			FILTER_SANITIZE_STRING
+		);
+
+		return 'POST' === $request_method;
+	}
 }
diff --git a/tests/phpunit/bootstrap.php b/tests/phpunit/bootstrap.php
index f1fe68d..08d8f45 100644
--- a/tests/phpunit/bootstrap.php
+++ b/tests/phpunit/bootstrap.php
@@ -42,7 +42,7 @@
 /**
  * Plugin version.
  */
-define( 'CYR_TO_LAT_TEST_VERSION', '5.2.2' );
+const CYR_TO_LAT_TEST_VERSION = '5.2.3';
 
 /**
  * Path to the plugin dir.
diff --git a/tests/phpunit/tests/class-test-main.php b/tests/phpunit/tests/class-test-main.php
index 54ebf9d..01fb9be 100644
--- a/tests/phpunit/tests/class-test-main.php
+++ b/tests/phpunit/tests/class-test-main.php
@@ -60,14 +60,14 @@ public function tearDown(): void {
 	public function test_constructor() {
 		$classname = Main::class;
 
-		// Test when requirements are met and not frontend.
+		// Test when requirements are met and allowed request.
 		$requirements_met = true;
-		$is_frontend      = false;
+		$is_allowed       = true;
 
 		$request = Mockery::mock( 'overload:' . Request::class );
-		$request->shouldReceive( 'is_frontend' )->with()->andReturnUsing(
-			function () use ( &$is_frontend ) {
-				return $is_frontend;
+		$request->shouldReceive( 'is_allowed' )->with()->andReturnUsing(
+			function () use ( &$is_allowed ) {
+				return $is_allowed;
 			}
 		);
 		$request->shouldReceive( 'is_cli' )->with()->andReturn( true );
@@ -125,8 +125,8 @@ function () use ( &$requirements_met ) {
 		self::assertNull( $this->get_protected_property( $mock, 'cli' ) );
 		self::assertNull( $this->get_protected_property( $mock, 'acf' ) );
 
-		// Test on frontend.
-		$is_frontend = true;
+		// Test on not allowed request.
+		$is_allowed = false;
 
 		// Get mock, without the constructor being called.
 		$mock = $this->getMockBuilder( $classname )->disableOriginalConstructor()->getMock();
@@ -153,7 +153,7 @@ function () use ( &$requirements_met ) {
 	 */
 	public function test_init() {
 		$request = Mockery::mock( Request::class );
-		$request->shouldReceive( 'is_frontend' )->andReturn( false );
+		$request->shouldReceive( 'is_allowed' )->andReturn( true );
 		$request->shouldReceive( 'is_cli' )->andReturn( false );
 
 		$subject = Mockery::mock( Main::class )->makePartial();
@@ -164,13 +164,13 @@ public function test_init() {
 	}
 
 	/**
-	 * Test init() on frontend
+	 * Test init() on allowed request.
 	 *
 	 * @throws ReflectionException ReflectionException.
 	 */
-	public function test_init_on_frontend() {
+	public function test_init_on_allowed_request() {
 		$request = Mockery::mock( Request::class );
-		$request->shouldReceive( 'is_frontend' )->andReturn( true );
+		$request->shouldReceive( 'is_allowed' )->andReturn( false );
 
 		$subject = Mockery::mock( Main::class )->makePartial();
 		$this->set_protected_property( $subject, 'request', $request );
@@ -186,7 +186,7 @@ public function test_init_on_frontend() {
 	 */
 	public function test_init_with_cli_error() {
 		$request = Mockery::mock( Request::class );
-		$request->shouldReceive( 'is_frontend' )->andReturn( false );
+		$request->shouldReceive( 'is_allowed' )->andReturn( true );
 		$request->shouldReceive( 'is_cli' )->andReturn( true );
 
 		$subject = Mockery::mock( Main::class )->makePartial();
@@ -213,7 +213,7 @@ function () {
 	 */
 	public function test_init_with_cli() {
 		$request = Mockery::mock( Request::class );
-		$request->shouldReceive( 'is_frontend' )->andReturn( false );
+		$request->shouldReceive( 'is_allowed' )->andReturn( true );
 		$request->shouldReceive( 'is_cli' )->andReturn( true );
 
 		$subject = Mockery::mock( Main::class )->makePartial();
@@ -951,11 +951,21 @@ public function test_pll_locale_filter_with_rest() {
 		$pll_locale = 'ru';
 		$data       = '';
 
-		$request = Mockery::mock( Request::class );
-		$request->shouldReceive( 'is_rest' )->andReturn( true );
-
 		$subject = Mockery::mock( Main::class )->makePartial();
-		$this->set_protected_property( $subject, 'request', $request );
+
+		FunctionMocker::replace(
+			'defined',
+			function ( $constant_name ) {
+				return 'REST_REQUEST' === $constant_name;
+			}
+		);
+
+		FunctionMocker::replace(
+			'constant',
+			function ( $name ) {
+				return 'REST_REQUEST' === $name;
+			}
+		);
 
 		$rest_server = new WP_REST_Server();
 		WP_Mock::userFunction( 'rest_get_server' )->andReturn( $rest_server );
@@ -973,16 +983,16 @@ function () use ( &$data ) {
 		self::assertSame( $pll_locale, $subject->pll_locale_filter( $locale ) );
 
 		// Test that result is cached.
-		$request->shouldReceive( 'is_rest' )->andReturn( false );
+		FunctionMocker::replace( 'defined' );
 		self::assertSame( $pll_locale, $subject->pll_locale_filter( $locale ) );
 	}
 
 	/**
-	 * Test pll_locale_filter() on frontend.
+	 * Test pll_locale_filter() on allowed request.
 	 *
 	 * @throws ReflectionException ReflectionException.
 	 */
-	public function test_pll_locale_filter_on_frontend() {
+	public function test_pll_locale_filter_on_allowed_request() {
 		$locale = 'en_US';
 
 		$request = Mockery::mock( Request::class );
diff --git a/tests/phpunit/tests/class-test-request.php b/tests/phpunit/tests/class-test-request.php
index c22ca56..28a43ff 100644
--- a/tests/phpunit/tests/class-test-request.php
+++ b/tests/phpunit/tests/class-test-request.php
@@ -28,11 +28,43 @@ class Test_Request extends Cyr_To_Lat_TestCase {
 	 */
 	public function tearDown(): void {
 		// phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited
-		unset( $_SERVER['REQUEST_URI'], $GLOBALS['wp_rewrite'] );
+		unset( $_SERVER['REQUEST_URI'], $_SERVER['REQUEST_METHOD'], $GLOBALS['wp_rewrite'] );
 
 		parent::tearDown();
 	}
 
+	/**
+	 * Test is_allowed().
+	 *
+	 * @param bool $frontend Is frontend.
+	 * @param bool $post     Is POST.
+	 * @param bool $expected Expected.
+	 *
+	 * @dataProvider dp_test_is_allowed
+	 * @noinspection PhpUndefinedMethodInspection
+	 */
+	public function test_is_allowed( $frontend, $post, $expected ) {
+		$subject = Mockery::mock( Request::class )->makePartial()->shouldAllowMockingProtectedMethods();
+		$subject->shouldReceive( 'is_frontend' )->with()->andReturn( $frontend );
+		$subject->shouldReceive( 'is_post' )->with()->andReturn( $post );
+
+		self::assertSame( $expected, $subject->is_allowed() );
+	}
+
+	/**
+	 * Data provider for test_is_allowed().
+	 *
+	 * @return array
+	 */
+	public function dp_test_is_allowed() {
+		return [
+			[ false, false, true ],
+			[ false, true, true ],
+			[ true, false, false ],
+			[ true, true, true ],
+		];
+	}
+
 	/**
 	 * Test is_frontend().
 	 *
@@ -239,4 +271,20 @@ public function dp_test_get_rest_route() {
 			'some request' => [ '/some-request', '' ],
 		];
 	}
+
+	/**
+	 * Test is_post().
+	 */
+	public function test_is_post() {
+		WP_Mock::passthruFunction( 'wp_unslash' );
+
+		$subject = new Request();
+		self::assertFalse( $subject->is_post() );
+
+		$_SERVER['REQUEST_METHOD'] = 'some';
+		self::assertFalse( $subject->is_post() );
+
+		$_SERVER['REQUEST_METHOD'] = 'POST';
+		self::assertTrue( $subject->is_post() );
+	}
 }