Is pouring hot stock into a blender safe? I have a "ThermoResist Glass Blender" attached to a mixer. It is supposed to be safe for blending hot liquids. I'm rather new at this and I'm not sure about how is it supposed to be used and how hot can the liquids be.

Can I prepare stock for soup over a stove top, cook vegetables in it, then pour it directly into the blender's goblet and mix?
Yes. At the link you provided in the specifications section, it says "Capacity: 1.6 quarts cold liquids; 1.2 quarts hot liquids". The word "hot" is a bit arbitrary, but stock will be fine.

Also, it's called ThermoResist.