diff -r 34716fd837a4 -r be944660c56a wp/wp-admin/includes/class-pclzip.php
--- a/wp/wp-admin/includes/class-pclzip.php	Tue Dec 15 15:52:01 2020 +0100
+++ b/wp/wp-admin/includes/class-pclzip.php	Wed Sep 21 18:19:35 2022 +0200
@@ -1171,7 +1171,7 @@
     $this->privErrorReset();
 
     // ----- Look if the $p_archive is a PclZip object
-    if ((is_object($p_archive)) && (get_class($p_archive) == 'pclzip'))
+    if (is_object($p_archive) && $p_archive instanceof pclzip)
     {
 
       // ----- Duplicate the archive
@@ -1235,7 +1235,7 @@
     }
 
     // ----- Look if the $p_archive_to_add is a PclZip object
-    if ((is_object($p_archive_to_add)) && (get_class($p_archive_to_add) == 'pclzip'))
+    if (is_object($p_archive_to_add) && $p_archive_to_add instanceof pclzip)
     {
 
       // ----- Merge the archive
@@ -2674,7 +2674,12 @@
         }
 
         // ----- Read the file content
-        $v_content = @fread($v_file, $p_header['size']);
+        if ($p_header['size'] > 0) {
+          $v_content = @fread($v_file, $p_header['size']);
+        }
+        else {
+          $v_content = '';
+        }
 
         // ----- Close the file
         @fclose($v_file);
@@ -3884,7 +3889,12 @@
 
 
             // ----- Read the compressed file in a buffer (one shot)
-            $v_buffer = @fread($this->zip_fd, $p_entry['compressed_size']);
+            if ($p_entry['compressed_size'] > 0) {
+              $v_buffer = @fread($this->zip_fd, $p_entry['compressed_size']);
+            }
+            else {
+              $v_buffer = '';
+            }
 
             // ----- Decompress the file
             $v_file_content = @gzinflate($v_buffer);
@@ -4096,7 +4106,12 @@
         if ($p_entry['compressed_size'] == $p_entry['size']) {
 
           // ----- Read the file in a buffer (one shot)
-          $v_buffer = @fread($this->zip_fd, $p_entry['compressed_size']);
+          if ($p_entry['compressed_size'] > 0) {
+            $v_buffer = @fread($this->zip_fd, $p_entry['compressed_size']);
+          }
+          else {
+            $v_buffer = '';
+          }
 
           // ----- Send the file to the output
           echo $v_buffer;
@@ -4105,7 +4120,12 @@
         else {
 
           // ----- Read the compressed file in a buffer (one shot)
-          $v_buffer = @fread($this->zip_fd, $p_entry['compressed_size']);
+          if ($p_entry['compressed_size'] > 0) {
+            $v_buffer = @fread($this->zip_fd, $p_entry['compressed_size']);
+          }
+          else {
+            $v_buffer = '';
+          }
 
           // ----- Decompress the file
           $v_file_content = gzinflate($v_buffer);
@@ -4209,12 +4229,22 @@
         if ($p_entry['compression'] == 0) {
 
           // ----- Reading the file
-          $p_string = @fread($this->zip_fd, $p_entry['compressed_size']);
+          if ($p_entry['compressed_size'] > 0) {
+            $p_string = @fread($this->zip_fd, $p_entry['compressed_size']);
+          }
+          else {
+            $p_string = '';
+          }
         }
         else {
 
           // ----- Reading the file
-          $v_data = @fread($this->zip_fd, $p_entry['compressed_size']);
+          if ($p_entry['compressed_size'] > 0) {
+            $v_data = @fread($this->zip_fd, $p_entry['compressed_size']);
+          }
+          else {
+            $v_data = '';
+          }
 
           // ----- Decompress the file
           if (($p_string = @gzinflate($v_data)) === FALSE) {