The box got crushed during shipping and the contents spilled out.

Literal

Shipping-during [in-に] box [subject-が] crushed contents [subject-が] popped-out.

拉げる (ひしゃげる, 'to be crushed/squashed') uses a rare kanji reading. 中身 ('contents, inside') + とび出す ('to pop/fly out') is a compound verb for things bursting out. 輸送中に ('during shipping') sets the scene. Two events chained without a connective — the crushing and the spilling are presented as a rapid cause-and-effect sequence.