Only users who have enabled device's accessibility setting are affected. Accessibility setting is for those who have visual or physical limitations, and is disabled by default. It is enabled by some apps such as TalkBack, ClockBack and so on.
The root cause of the issue is:
Proof of Concept: At present I do not have plans to disclose PoC for this issue.
Timeline: 2012/07/08 Reported to Google security team. 2012/09/12 Vender announced v18.0.1025308 2013/01/07 Disclosure of this advisory
Recommendation: Upgrade to the latest version.
Reference: http://googlechromereleases.blogspot.jp/2012/09/chrome-for-android-update.html https://code.google.com/p/chromium/issues/detail?id=144813