From the Urban Dictionary, via GeekPress:

When someone alters a Wikipedia article to win a specific argument, anyone who reads the false article before the "error" is corrected suffers from collateral misinformation.

[Example:] "I changed the scientific classification of red foxes last night in order to win an argument with Judy. I hope some stupid High School student didn't suffer from collateral misinformation."

And, no, this isn't a "real" phrase, in the sense of a phrase that is actually commonly used, even by some subculture (see this search).