Samsung May Be "World's biggest handset maker," but... They may also be the maker of the most exploitable handsets. These are all recent, major issues with Samsung handsets and tablets:
Support Galaxy S3 crashing when copying text to clipboard
That bug affects all Samsung tablets and handsets running ICS or JB, and, as one developer noted, may introduce a security vulnerability. (This is the one that made me start looking into Samsung's customer service and product track record.)
Samsung Exynos 4 Exploit Discovered: Root And Full Access To RAM Possible In A Single App
Essentially any app can root many Samsung handsets and tablets without the user being any the wiser. Samsung has promised a fix "soon."
This is a good one:
The Superbrick Nightmare Or How Samsung Screwed All Galaxy Note Owners
Imagine: A brand-new, allegedly state-of-the-art device, you get an update, do a factory reset (for whatever reason) and find your new device is hopelessly and irretrievably bricked. Wow.
Major security vulnerability in some Samsung phones could trigger factory reset via web page
You visit a particular web page, your phone factory resets, and there goes all your stuff. Cool
I don't know... I think I'd think twice before buying any Samsung mobile devices in the near future. Their hardware may be great, but their software quality appears to leave a lot to be desired.