  Online social media represent an oftentimes unique source of information, and
having access to reliable and unbiased content is crucial, especially during
crises and contentious events. We study the spread of propaganda and
misinformation that circulated on Facebook and Twitter during the first few
months of the Russia-Ukraine conflict. By leveraging two large datasets of
millions of social media posts, we estimate the prevalence of Russian
propaganda and low-credibility content on the two platforms, describing
temporal patterns and highlighting the disproportionate role played by
superspreaders in amplifying unreliable content. We infer the political leaning
of Facebook pages and Twitter users sharing propaganda and misinformation, and
observe they tend to be more right-leaning than the average. By estimating the
amount of content moderated by the two platforms, we show that only about 8-15%
of the posts and tweets sharing links to Russian propaganda or untrustworthy
sources were removed. Overall, our findings show that Facebook and Twitter are
still vulnerable to abuse, especially during crises: we highlight the need to
urgently address this issue to preserve the integrity of online conversations.
