Word Press 3.3.1

I recently inherited responsibility for a Word Press blog that is updated weekly. Some content is available to the public; some requires a paid subscription. The owner is using v3.3.1.

When new limited-access info is posted, it is marked as Category:Subscription, and security set to Level 1 and higher.

We discovered today that if a user clicks on a public link, then erases part of the address (for instance, clicks on Today’s Post {domain.com/2012/sept/10}, then erases back to domain.com/2012/), all of the archived posts, public and subscription, are accessible.

Is this something that would be addressed by updating? Is there another way to keep archived subscription areas accessible only to subscribers?

The first time i used WP was about 3 weeks ago, so i’m not at all familiar at all with how it works, or what options are built in. I don’t know whether any plugins are installed, but i doubt there are. I do know that there are better ways to do it, but please limit answers to whether anything can be done with the setup the way it is. Thanks in advance for any info or help.

WP doesn’t support paid subscriptions without a plugin.