The Apple Airport Extreme has the OpenSSL Heartbleed bug. The update notice indicates that only newer models with certain features are vulnerable to this:
Only AirPort Extreme and AirPort Time Capsule base stations with 802.11ac are affected, and only if they have Back to My Mac or Send Diagnostics enabled. Other AirPort base stations are not impacted by this issue.
If you have one of these I recommend updating the firmware to version 7.7.3 even if you don’t have those features enabled.