One of the benefits of being a pure Joomla Consultant is that I get to see trends emerging over multiple platforms, sites and systems that an individual Joomla user or admin would not spot.
For example, today I have been asked by 5 independant customers worldwide to investigate why their site was just displaying the words “Restricted Access” on their Joomla frontpage.
Well, after a little while debugging I found that each one had been hacked, and had been hacked the same way with a new type of hack I had not seen before. They also were not running the very latest version of Joomla 1.5.x (Which is 1.5.9) !!!
I’m not going to go into detail about this hack in my blog post – enough to say though that if you just see those two dreaded words “Restricted Access” then consider you have been hacked and employ a professional to debug and fix your site.
BACKUP NOW – and make sure you are running the latest Joomla version too! Be Safe, Be Secure 
First off, What’s the “vulnerability” that you found (at least have you reported it to the Joomla Security Team for verification)?
Secondly, how many versions of 1.5.9 are there?
Third, “Restricted Access” has been popping up due to the SEF patch not being updated. Remove the patch, and viola it all works.
Mr IrcMaxwell
I think you misread my post 
I’m not saying there is a *new* vulnerability in Joomla 1.5.9 
I’m saying that these customers all had a version less than 1.5.9. There is no need for the JSST to investigate this issue – I believe the root entry point for this particular attack is the admin password reset issue thats already fixed in 1.5.9
I have updated the post to clarify the 1.5.9 versions – I know there is only one version of 1.5.9, I meant to say the latest “1.5.x” version
I have emailed you slightly more details.
I have not seen the SEF Patch on any customers sites…
So, here I am hoping to find a fix, yet I find a “make sure you employ me to change a few lines of code – you’ll be sorted!”
I guess not.
Sorry to be so negative, but maybe you could share a fix for those who are in need of one. Not to push people in spending money on Joomla Consultant to debug a totally free CMS…
There is NO quick fix
a hacked website needs professional care to ensure all traces of a hack are removed, your system patched, and preventative procedures implemented 
Here is a check-list of best practices you could follow BEFORE you are hacked. http://docs.joomla.org/Category:Security_Checklist
But……I receive this message on my test site. It is not live and only available on my local machine. I use the site to try out various extensions. Are you saying that my test site has been compromised if I see this message?