Update blog engine again

Here are some of the notable issues that are fixed in beta 1.

• Certain themes were calling get_categories() in such a way that it would fail in 2.8. 2.8.1 works around this so these themes won’t have to change.
• Dashboard memory usage is reduced. Some people were running out of memory when loading the dashboard, resulting in an incomplete page.
• The automatic upgrade no longer accidentally deletes files when cleaning up from a failed upgrade.
• A problem where the rich text editor wasn’t being loaded due to compression issues has been worked around.
• Extra security has been put in place to better protect you from plugins that do not do explicit permission checks 

Official Link: www.wordpress.org