Targeted spread of fake news on social media, automating websites that appear on the surface like local news stations that don't exist in real life, ...
EDIT: also manipulation of wikipedia articles using proxies and hard to verify sources.
There is a lot of rules and guidelines around sourcing for Wikipedia articles. Some random website that isn't generally recognized as a credible source can't (shouldn't) be used as a source. Even reliable first party sources are discouraged.
The downside of course is even generally accepted credible websites still display tremendous bias, which leads to tremendous bias in Wikipedia in general as editors pick and choose sources and silence dissenters.
EDIT: also manipulation of wikipedia articles using proxies and hard to verify sources.