I have csv file with polygon geometry stored in "extent' field (not stored in x,y coordinates but in encrypted format), need to convert the same to polygon shape file. Any suggestions please

What are the results when you add a GeometryReplacer and try the different Geometry Encodings?

Hopefully one of the encodings will do the trick...

Edit:  Probably the encoding is OGC Well Known Binary.

Thanks, it worked out with OGC Well Known Binary encoding...