...saw the blog about 1.5.19 being released, then as I was checking the Joomla! mothership tonight, I saw that they cut 1.5.20 this evening:
The Joomla Project announces the immediate availability of Joomla 1.5.20 [senu takaa]. This is a security release that addresses issues with the Joomla 1.5.19 packages. We recommend users upgrade immediately.