Mozilla released Firefox 3.5.8 on 17th Feb 2010, with some minor updates on security issues and other known issues. The update actually covers several fixes for unexpected crashes.
Security issues fixed in this version:
MFSA 2010-05 XSS hazard using SVG document and binary Content-Type
MFSA 2010-04 XSS due to window.dialogArguments being readable cross-domain
MFSA 2010-03 Use-after-free crash in HTML parser
MFSA 2010-02 Web Worker Array Handling Heap Corruption Vulnerability
MFSA 2010-01 Crashes with evidence of memory corruption (rv:184.108.40.206/ 220.127.116.11)
Updates: And yeah, you can also download the latest 3.6 version, which is officially released and no longer in Beta.