I found that my blog posts are inserted lot’s of ad links, I’m using WordPress 2.9.2, is there a known security vulnerability in it?
A screenshot : I post some codes on my blog, the ad links are inserted into them.
I delete them by hand several days ago, and I found that they’re back again!
Looks like you’ve been hacked. In all fairness, you’re running a version that is over a year old – it’s always best practice to upgrade as soon as you can.
I would advise reading through the FAQ on the codex. I also stumbled across this rather concise step-by-step, though I would advise it’s for the intermediate user (use of SQL and FTP is required).