diff --git a/CMakeLists.txt b/CMakeLists.txt
index 741bc676c1..e5ef9e78cb 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -736,8 +736,15 @@ if(ENABLE_FLAKE8 AND PYTHON_DEFAULT_AVAILABLE)
     include("${CMAKE_CURRENT_LIST_DIR}/cmake/FindFlake8.cmake")
   endif()
   if(FLAKE8_FOUND)
+    list(APPEND OPENCV_FLAKE8_EXCLUDES ".git" "__pycache__" "config.py" "*.config.py" "config-*.py")
+    list(APPEND OPENCV_FLAKE8_EXCLUDES "svgfig.py")  # 3rdparty
+    if(NOT PYTHON3_VERSION_STRING VERSION_GREATER 3.6)
+      # Python 3.6+ (PEP 526): variable annotations (type hints)
+      list(APPEND OPENCV_FLAKE8_EXCLUDES "samples/dnn/dnn_model_runner/dnn_conversion/common/test/configs")
+    endif()
+    string(REPLACE ";" "," OPENCV_FLAKE8_EXCLUDES_STR "${OPENCV_FLAKE8_EXCLUDES}")
     add_custom_target(check_flake8
-        COMMAND "${FLAKE8_EXECUTABLE}" . --count --select=E9,E901,E999,F821,F822,F823 --show-source --statistics --exclude='.git,__pycache__,*.config.py,svgfig.py'
+        COMMAND "${FLAKE8_EXECUTABLE}" . --count --select=E9,E901,E999,F821,F822,F823 --show-source --statistics --exclude='${OPENCV_FLAKE8_EXCLUDES_STR}'
         WORKING_DIRECTORY "${OpenCV_SOURCE_DIR}"
         COMMENT "Running flake8"
     )
diff --git a/cmake/FindFlake8.cmake b/cmake/FindFlake8.cmake
index b18225a011..8063571393 100644
--- a/cmake/FindFlake8.cmake
+++ b/cmake/FindFlake8.cmake
@@ -12,9 +12,11 @@
 
 find_host_program(FLAKE8_EXECUTABLE flake8 PATHS /usr/bin)
 
-if(FLAKE8_EXECUTABLE)
-  execute_process(COMMAND ${FLAKE8_EXECUTABLE} --version OUTPUT_VARIABLE FLAKE8_VERSION_RAW ERROR_QUIET)
-  if(FLAKE8_VERSION_RAW MATCHES "^([0-9\\.]+[0-9])")
+if(FLAKE8_EXECUTABLE AND NOT DEFINED FLAKE8_VERSION)
+  execute_process(COMMAND ${FLAKE8_EXECUTABLE} --version RESULT_VARIABLE _result OUTPUT_VARIABLE FLAKE8_VERSION_RAW)
+  if(NOT _result EQUAL 0)
+    ocv_clear_vars(FLAKE8_EXECUTABLE FLAKE8_VERSION)
+  elseif(FLAKE8_VERSION_RAW MATCHES "^([0-9\\.]+[0-9])")
     set(FLAKE8_VERSION "${CMAKE_MATCH_1}")
   else()
     set(FLAKE8_VERSION "unknown")
@@ -22,6 +24,9 @@ if(FLAKE8_EXECUTABLE)
 endif()
 
 include(FindPackageHandleStandardArgs)
-FIND_PACKAGE_HANDLE_STANDARD_ARGS(Flake8 DEFAULT_MSG FLAKE8_EXECUTABLE)
+FIND_PACKAGE_HANDLE_STANDARD_ARGS(Flake8
+    REQUIRED_VARS FLAKE8_EXECUTABLE
+    VERSION_VAR FLAKE8_VERSION
+)
 
 mark_as_advanced(FLAKE8_EXECUTABLE FLAKE8_VERSION)
diff --git a/cmake/FindPylint.cmake b/cmake/FindPylint.cmake
index 7e26fe246e..5731ba493a 100644
--- a/cmake/FindPylint.cmake
+++ b/cmake/FindPylint.cmake
@@ -12,9 +12,11 @@
 
 find_host_program(PYLINT_EXECUTABLE pylint PATHS /usr/bin)
 
-if(PYLINT_EXECUTABLE)
-  execute_process(COMMAND ${PYLINT_EXECUTABLE} --version OUTPUT_VARIABLE PYLINT_VERSION_RAW ERROR_QUIET)
-  if(PYLINT_VERSION_RAW MATCHES "pylint([^,]*) ([0-9\\.]+[0-9])")
+if(PYLINT_EXECUTABLE AND NOT DEFINED PYLINT_VERSION)
+  execute_process(COMMAND ${PYLINT_EXECUTABLE} --version RESULT_VARIABLE _result OUTPUT_VARIABLE PYLINT_VERSION_RAW)
+  if(NOT _result EQUAL 0)
+    ocv_clear_vars(PYLINT_EXECUTABLE PYLINT_VERSION)
+  elseif(PYLINT_VERSION_RAW MATCHES "pylint([^,]*) ([0-9\\.]+[0-9])")
     set(PYLINT_VERSION "${CMAKE_MATCH_2}")
   else()
     set(PYLINT_VERSION "unknown")
@@ -22,6 +24,9 @@ if(PYLINT_EXECUTABLE)
 endif()
 
 include(FindPackageHandleStandardArgs)
-FIND_PACKAGE_HANDLE_STANDARD_ARGS(Pylint DEFAULT_MSG PYLINT_EXECUTABLE)
+FIND_PACKAGE_HANDLE_STANDARD_ARGS(Pylint
+    REQUIRED_VARS PYLINT_EXECUTABLE
+    VERSION_VAR PYLINT_VERSION
+)
 
 mark_as_advanced(PYLINT_EXECUTABLE PYLINT_VERSION)
diff --git a/modules/core/include/opencv2/core/hal/intrin_wasm.hpp b/modules/core/include/opencv2/core/hal/intrin_wasm.hpp
index 2f835bb9f8..b4178af8b7 100644
--- a/modules/core/include/opencv2/core/hal/intrin_wasm.hpp
+++ b/modules/core/include/opencv2/core/hal/intrin_wasm.hpp
@@ -1266,8 +1266,9 @@ OPENCV_HAL_IMPL_WASM_BIN_FUNC(v_uint8x16, v_sub_wrap, wasm_i8x16_sub)
 OPENCV_HAL_IMPL_WASM_BIN_FUNC(v_int8x16, v_sub_wrap, wasm_i8x16_sub)
 OPENCV_HAL_IMPL_WASM_BIN_FUNC(v_uint16x8, v_sub_wrap, wasm_i16x8_sub)
 OPENCV_HAL_IMPL_WASM_BIN_FUNC(v_int16x8, v_sub_wrap, wasm_i16x8_sub)
-#if (__EMSCRIPTEN_major__ * 1000000 + __EMSCRIPTEN_minor__ * 1000 + __EMSCRIPTEN_tiny__) >= (2000000)
+#if (__EMSCRIPTEN_major__ * 1000000 + __EMSCRIPTEN_minor__ * 1000 + __EMSCRIPTEN_tiny__) >= (1039012)
 // details: https://github.com/opencv/opencv/issues/18097 ( https://github.com/emscripten-core/emscripten/issues/12018 )
+// 1.39.12: https://github.com/emscripten-core/emscripten/commit/cd801d0f110facfd694212a3c8b2ed2ffcd630e2
 inline v_uint8x16 v_mul_wrap(const v_uint8x16& a, const v_uint8x16& b)
 {
     uchar a_[16], b_[16];
@@ -1275,7 +1276,7 @@ inline v_uint8x16 v_mul_wrap(const v_uint8x16& a, const v_uint8x16& b)
     wasm_v128_store(b_, b.val);
     for (int i = 0; i < 16; i++)
         a_[i] = (uchar)(a_[i] * b_[i]);
-    return wasm_v128_load(a_);
+    return v_uint8x16(wasm_v128_load(a_));
 }
 inline v_int8x16 v_mul_wrap(const v_int8x16& a, const v_int8x16& b)
 {
@@ -1284,7 +1285,7 @@ inline v_int8x16 v_mul_wrap(const v_int8x16& a, const v_int8x16& b)
     wasm_v128_store(b_, b.val);
     for (int i = 0; i < 16; i++)
         a_[i] = (schar)(a_[i] * b_[i]);
-    return wasm_v128_load(a_);
+    return v_int8x16(wasm_v128_load(a_));
 }
 #else
 OPENCV_HAL_IMPL_WASM_BIN_FUNC(v_uint8x16, v_mul_wrap, wasm_i8x16_mul)
@@ -1757,8 +1758,8 @@ inline v_uint64x2 v_popcount(const v_uint64x2& a)
     uint64 a_[2], b_[2] = { 0 };
     wasm_v128_store(a_, a.val);
     for (int i = 0; i < 16; i++)
-        b_[i / 8] += popCountTable[((uint8*)a_)[i]];
-    return wasm_v128_load(b_);
+        b_[i / 8] += popCountTable[((uint8_t*)a_)[i]];
+    return v_uint64x2(wasm_v128_load(b_));
 }
 inline v_uint8x16 v_popcount(const v_int8x16& a)
 { return v_popcount(v_reinterpret_as_u8(a)); }
@@ -1938,11 +1939,11 @@ inline v_int32x4 func(const v_float64x2& a) \
     double a_[2]; \
     wasm_v128_store(a_, a.val); \
     int c_[4]; \
-    c_[0] = cfunc(a_[i]); \
-    c_[1] = cfunc(a_[i]); \
+    c_[0] = cfunc(a_[0]); \
+    c_[1] = cfunc(a_[1]); \
     c_[2] = 0; \
     c_[3] = 0; \
-    return wasm_v128_load(c_); \
+    return v_int32x4(wasm_v128_load(c_)); \
 }
 
 OPENCV_HAL_IMPL_WASM_MATH_FUNC(v_round, cvRound)
@@ -1960,7 +1961,7 @@ inline v_int32x4 v_round(const v_float64x2& a, const v_float64x2& b)
     c_[1] = cvRound(a_[1]);
     c_[2] = cvRound(b_[0]);
     c_[3] = cvRound(b_[1]);
-    return wasm_v128_load(c_);
+    return v_int32x4(wasm_v128_load(c_));
 }
 
 #define OPENCV_HAL_IMPL_WASM_TRANSPOSE4x4(_Tpvec, suffix) \
@@ -2461,7 +2462,7 @@ inline v_float32x4 v_cvt_f32(const v_float64x2& a)
     c_[1] = (float)(a_[1]);
     c_[2] = 0;
     c_[3] = 0;
-    return wasm_v128_load(c_);
+    return v_float32x4(wasm_v128_load(c_));
 }
 
 inline v_float32x4 v_cvt_f32(const v_float64x2& a, const v_float64x2& b)
@@ -2474,7 +2475,7 @@ inline v_float32x4 v_cvt_f32(const v_float64x2& a, const v_float64x2& b)
     c_[1] = (float)(a_[1]);
     c_[2] = (float)(b_[0]);
     c_[3] = (float)(b_[1]);
-    return wasm_v128_load(c_);
+    return v_float32x4(wasm_v128_load(c_));
 }
 
 inline v_float64x2 v_cvt_f64(const v_int32x4& a)
@@ -2488,7 +2489,7 @@ inline v_float64x2 v_cvt_f64(const v_int32x4& a)
     double c_[2];
     c_[0] = (double)(a_[0]);
     c_[1] = (double)(a_[1]);
-    return wasm_v128_load(c_);
+    return v_float64x2(wasm_v128_load(c_));
 #endif
 }
 
@@ -2503,7 +2504,7 @@ inline v_float64x2 v_cvt_f64_high(const v_int32x4& a)
     double c_[2];
     c_[0] = (double)(a_[2]);
     c_[1] = (double)(a_[3]);
-    return wasm_v128_load(c_);
+    return v_float64x2(wasm_v128_load(c_));
 #endif
 }
 
@@ -2514,7 +2515,7 @@ inline v_float64x2 v_cvt_f64(const v_float32x4& a)
     double c_[2];
     c_[0] = (double)(a_[0]);
     c_[1] = (double)(a_[1]);
-    return wasm_v128_load(c_);
+    return v_float64x2(wasm_v128_load(c_));
 }
 
 inline v_float64x2 v_cvt_f64_high(const v_float32x4& a)
@@ -2524,7 +2525,7 @@ inline v_float64x2 v_cvt_f64_high(const v_float32x4& a)
     double c_[2];
     c_[0] = (double)(a_[2]);
     c_[1] = (double)(a_[3]);
-    return wasm_v128_load(c_);
+    return v_float64x2(wasm_v128_load(c_));
 }
 
 inline v_float64x2 v_cvt_f64(const v_int64x2& a)
@@ -2537,7 +2538,7 @@ inline v_float64x2 v_cvt_f64(const v_int64x2& a)
     double c_[2];
     c_[0] = (double)(a_[0]);
     c_[1] = (double)(a_[1]);
-    return wasm_v128_load(c_);
+    return v_float64x2(wasm_v128_load(c_));
 #endif
 }
 
@@ -2757,7 +2758,7 @@ inline v_float32x4 v_load_expand(const float16_t* ptr)
     float a[4];
     for (int i = 0; i < 4; i++)
         a[i] = ptr[i];
-    return wasm_v128_load(a);
+    return v_float32x4(wasm_v128_load(a));
 }
 
 inline void v_pack_store(float16_t* ptr, const v_float32x4& v)
diff --git a/modules/core/include/opencv2/core/utils/tls.hpp b/modules/core/include/opencv2/core/utils/tls.hpp
index 697a7b0340..124caebc85 100644
--- a/modules/core/include/opencv2/core/utils/tls.hpp
+++ b/modules/core/include/opencv2/core/utils/tls.hpp
@@ -5,7 +5,9 @@
 #ifndef OPENCV_UTILS_TLS_HPP
 #define OPENCV_UTILS_TLS_HPP
 
-#include <opencv2/core/utility.hpp>
+#ifndef OPENCV_CORE_UTILITY_H
+#error "tls.hpp must be included after opencv2/core/utility.hpp or opencv2/core.hpp"
+#endif
 
 namespace cv {
 
diff --git a/modules/python/src2/cv2.cpp b/modules/python/src2/cv2.cpp
index 1e7bfd62a8..abe7253fce 100644
--- a/modules/python/src2/cv2.cpp
+++ b/modules/python/src2/cv2.cpp
@@ -32,13 +32,14 @@
 
 #include <numpy/ndarrayobject.h>
 
+#include "opencv2/opencv_modules.hpp"
+#include "opencv2/core.hpp"
 #include "opencv2/core/utils/configuration.private.hpp"
 #include "opencv2/core/utils/logger.hpp"
 #include "opencv2/core/utils/tls.hpp"
 
 #include "pyopencv_generated_include.h"
 #include "opencv2/core/types_c.h"
-#include "opencv2/opencv_modules.hpp"
 #include "pycompat.hpp"
 #include <map>
 
diff --git a/modules/python/test/test.py b/modules/python/test/test.py
index 97c2144303..a40c6c5d7e 100755
--- a/modules/python/test/test.py
+++ b/modules/python/test/test.py
@@ -34,8 +34,8 @@ def load_tests(loader, tests, pattern):
     else:
         print('WARNING: OpenCV tests config file ({}) is missing, running subset of tests'.format(config_file))
 
-    tests_pattern = os.environ.get('OPENCV_PYTEST_FILTER', 'test_') + '*.py'
-    if tests_pattern != 'test_*py':
+    tests_pattern = os.environ.get('OPENCV_PYTEST_FILTER', 'test_*') + '.py'
+    if tests_pattern != 'test_*.py':
         print('Tests filter: {}'.format(tests_pattern))
 
     processed = set()
diff --git a/samples/dnn/tf_text_graph_ssd.py b/samples/dnn/tf_text_graph_ssd.py
index 46a9064738..dbdee6ea9f 100644
--- a/samples/dnn/tf_text_graph_ssd.py
+++ b/samples/dnn/tf_text_graph_ssd.py
@@ -122,7 +122,6 @@ def createSSDGraph(modelPath, configPath, outputPath):
     print('Input image size: %dx%d' % (image_width, image_height))
 
     # Read the graph.
-    _inpNames = ['image_tensor']
     outNames = ['num_detections', 'detection_scores', 'detection_boxes', 'detection_classes']
 
     writeTextGraph(modelPath, outputPath, outNames)
@@ -247,6 +246,15 @@ def createSSDGraph(modelPath, configPath, outputPath):
     graph_def.node[1].input.append(graph_def.node[0].name)
     graph_def.node[1].input.append(weights)
 
+    # check and correct the case when preprocessing block is after input
+    preproc_id = "Preprocessor/"
+    if graph_def.node[2].name.startswith(preproc_id) and \
+        graph_def.node[2].input[0].startswith(preproc_id):
+
+        if not any(preproc_id in inp for inp in graph_def.node[3].input):
+            graph_def.node[3].input.insert(0, graph_def.node[2].name)
+
+
     # Create SSD postprocessing head ###############################################
 
     # Concatenate predictions of classes, predictions of bounding boxes and proposals.
diff --git a/samples/python/hist.py b/samples/python/hist.py
index 4e73f0bc65..4c2c1ad395 100755
--- a/samples/python/hist.py
+++ b/samples/python/hist.py
@@ -76,7 +76,7 @@ def main():
     a - show histogram for color image in curve mode \n
     b - show histogram in bin mode \n
     c - show equalized histogram (always in bin mode) \n
-    d - show histogram for color image in curve mode \n
+    d - show histogram for gray image in curve mode \n
     e - show histogram for a normalized image in curve mode \n
     Esc - exit \n
     ''')