Problem with adding mesh whenever i add a mesh on another object, 
the object is always linked : 
when i add a cylinder on a cube and whenever i scale or transform the cylinder also the cube will scale or move, but just in the current project, maybe i changed somethings but i dont know what.
Means by which this could happen:

Object added in 'edit' mode then scale/move/rotate in 'object' mode 

Is the object 'parented' to it? 

Constraints or drivers can also affect loc/rot/scale.