Map the mouse button 4 and 5 to browser's back and forward commands using Karabiner

private.xml

<?xml version="1.0"?>
<root>
  <devicevendordef>
    <vendorname>DELUX</vendorname>
    <vendorid>0x093a</vendorid>
  </devicevendordef>

  <deviceproductdef>
    <productname>DELUX_M618</productname>
    <productid>0x2521</productid>
  </deviceproductdef>

  <item>
    <name>Delux M618</name>
    <item>
      <name>Mouse navigate back</name>
      <identifier>private.delux_m618_nav_back</identifier>
      <device_only>DeviceVendor::DELUX, DeviceProduct::DELUX_M618</device_only>
      <autogen>
        __KeyToKey__
        PointingButton::BUTTON5,
        KeyCode::BRACKET_LEFT, ModifierFlag::COMMAND_L,
        Option::NOREPEAT
      </autogen>
    </item>

    <item>
      <name>Mouse navigate forward</name>
      <identifier>private.delux_m618_nav_forward</identifier>
      <device_only>DeviceVendor::DELUX, DeviceProduct::DELUX_M618</device_only>
      <autogen>
        __KeyToKey__
        PointingButton::BUTTON4,
        KeyCode::BRACKET_RIGHT, ModifierFlag::COMMAND_L,
        Option::NOREPEAT
      </autogen>
    </item>
  </item>
</root>