Philips Hue lights and most other devices periodically receives firmware updates.
Using Hue Log, you can get a complete overview of all your devices to see which firmware version they are running, and if there are any updates available.
In the sidebar, under the Status section, click Firmware.
You see modal and the current firmware version, with the state indicating if there is a new version available.
State may be:
The most common reason why a firmware update is stuck at pending, is because the device is not connected (as indicated in the Connectivity column). Read more about how to use Hue Log to detect and fix connectivity issues.