I did some searching due to the other answer and found someone on XDA claiming that this is a Market/Play bug, and you're seeing it because the Market thinks one of your apps is actually that OJSC Mobile app.
Even better, I found this just-published story on The Verge:
Samsung has several pieces of software that it installs on it devices but that aren't in the Google Play store (for obvious reasons). However, every single Android app has an app name that identifies it on the Android system, in this case the "unique" name is com.seven.Z7, which identifies Samsung's email app. What appears to have happened is that Russian developer OJSC Mobile Telesystems gave that unique identifier to its "МТС Мобильная Почта" app, and so these Samsung devices were tricked into thinking it was an update to Samsung's email client. Since Google Play allows for automatic updating of all apps, it was installed on many devices.
I couldn't find the app in the Play Store anymore, so perhaps Google has taken it down to resolve this.
Below is the original version of this post, which would still be applicable in more normal circumstances.
If it's a system app for supporting Cyrillic text, which is what it sounds like, it could hardly be called malware. Crapware, perhaps, if you don't need it.
If you don't need it, then no need to update (unless you want to be rid of the notification, though in that case I recommend rooting and removing the app). No reason not to update either I'd say — you already have it on your device, so unless it's doing something nasty in the new version in particular then you've already been exposed to any dangers it may contain :P. Of course, updating will require more space on your device unless you are rooted and can entirely replace the original version with the update (normally the system keeps all original versions of system apps).