Sony has released a new Firmware Version to counter act the recent exploit found in firmware 2.0. The new update corrects the TIFF image exploit that allows the PSP to be downgraded to v1.5.
The update is available to NA and Japan at time of writing. The update is available using the Network Update feature on your PSP.
Note: Upgrading your firmware will mean you can no longer make use of the Firmware 2.0 exploit. Upgrade at your own will. But remember, no homebrew for you!