It looks as if the "buttons in clantag" epidemic that first plagued MW3 after it's release is back, even though the glitch was reportedly patched by Infinity Ward.
The fact that all of this is happening after the initial patch will surely piss people off.
If reports are true, this is happening on both the XBox 360 and the PS3.
How are they doing this?
This time, the hack/glitch isn't achieved via entering special characters into the clantag. Instead, the user downloads an external file gpd file that is injected into the user's XBox profile. My guess is that a similar route is taken on the PS3. My advice is not to try and do this as IW will ban anyone that is found to have buttons in their clantag. Is having an X or an O in your clantag really worth being banned? Also, the fact that an external hack is involved means that you are at risk of being banned by XBox Live, as it clearly breaches their terms of service.