select table privilege in postgres allows user to create index on the table

Hi,
I created a user and assigned select privilege on a table. The user can not
insert any data or add a field to the table. But, the user can create
indexes on the table despite having select only privileges. This becomes a
serious problem if the user can create unique indexes on the table where it
has select only privilege.

Can somebody update me on this, I guess other people must have noticed it.

Cheers
Shahid