POODLE could allow an attacker to hijack and decrypt the session cookie that identifies you to a service like Twitter or Google, and then take over your accounts without needing your password.
The attack works only on traffic sessions using SSLv3. Although this is an old protocol that has been replaced in many client and server configurations with TLS (Transport Layer Security), many browser clients and web servers that use TLS for connections still support SSLv3. Some products and browsers, like Internet Explorer 6 for Windows XP, only use SSLv3. There are also clients that support SSLv3 as an alternative to use whenever a TLS connection to a web server fails. An attacker could exploit this compatibility to downgrade a connection to SSLv3 and then conduct the POODLE attack to hijack your session