Script Extensions are not working.

In what edition or version?
Just test it on Desktop Edition v25.9.30.2859 and ScriptExtension work fine..
This script not working
``Blockquote
Inventory Section
Item Name:<label for="averageCost">Average Cost:</label>
<input type="text" id="averageCost" name="averageCost" class="disabled" readonly> <!-- Disabled and Readonly -->
<button type="submit">Submit</button>
``

