From MoodleDocs

Release date: 8th June, 2010

Here is the full list of issues fixed in 1.9.9

Highlights

• Some general minor bugs fixed in different areas.
• Four security fixes (see below).

Security issues

Some of these vulnerabilities are potentially serious so we strongly recommend you upgrade.

Full details to be released soon.

• MSA-10-0010:
• MSA-10-0011:
• MSA-10-0012:
• MSA-10-0013: