That looks like a urlencoded base64 string.
The data seems to be something unreadable so I dumped it in HEX:
67AB2915D96A0DA5CC8DDA034E232F3D2FF783C2009A65BF1AA4C70B
Some more hints that % sign is followed by two hexadecimal letters e.g. %2F is / that output ends with == with is very typically for base 64