After I had upgraded to WordPress 2.6, I went to view my site stats on the CyStats page. Strangely, after I had done that (and I didn't make any changes to my settings in CyStats), the following warning was displayed on every blog page, even when I was logged out:
Warning: unserialize() expects parameter 1 to be string, array given in [my-path]/wp-content/plugins/cystats/includes/cystats.class.php on line 97
[my-path] refers to my WP installation directory.
Why is this occurring? Could this be a bug in CyStats?