As is stated in the Patch Set Note that accompanies the Oracle Application Express 5.1.1 patch set:
- If you have Oracle Application Express release 5.1 installed, download the Oracle Application Express 5.1.1 patch set from My Oracle Support and apply it. Remember - patch number 25341386.
- If you have Oracle Application Express release 5.0.4 or earlier installed, download and install the entire Oracle Application Express 5.1.1 release from the Oracle Technology Network (OTN).
- If you do not have Oracle Application Express installed, download and install the entire Oracle Application Express 5.1.1 release from the Oracle Technology Network (OTN).
As usual, there are a large number of issues corrected in the Application Express 5.1.1 patch set (over 106!). You can see the full list in the 5.1.1 Patch Set Notes.