Bug introduced in 8.0

Hi all,

I have a new job and dba rol with PostgreSQL, they have installed
PostgreSQL 8.0.2, but I found this release have some bugs, fixed in
newer versions,
I interesting particulary on this bug:

"Fix bug introduced in 8.0 that could allow ReadBuffer to return an
already-used page as new, potentially causing loss of
recently-committed data (Tom)"
http://www.postgresql.org/docs/8.0/static/release-8-0-6.html

I know an upgrade is a best solution but it's impossible now for me (I
do not have authorization), my answer is, what exactly means this bug?
is serious?

sorry poor english.

Please help, thanks.

Sergio.