塞私货

Traditional (Taiwan): 塞私貨

sāisīhuò ㄙㄞ ㄙ ㄏㄨㄛˋ

    • to sneak one's own views or agenda into something supposed to be neutral

Character by character

Saying俗语俗語

Idiom惯用语 · Widely known

Literally
slip in private goods
Meaning
To sneak one's own views or agenda into something, such as a text, talk or lesson, that is supposed to be neutral. Critical.

Sources