Twitter CEO Jack Dorsey addresses students during a town hall at the Indian Institute of Technology (IIT) in New Delhi, India, November 12, 2018.

Twitter plunged just over 11 percent Thursday after a report from an investor group that called the company "toxic" to advertisers and investors.

Citron Research, led by investor Andrew Left, wrote that Twitter is "uninvestible" and "advertisers will soon be forced to take a hard look at all sponsorships with Twitter." The report followed the publication of an Amnesty International investigation earlier this week, which found that women are sent abusive messages on the platform every 30 seconds.

Left said in March that he was short Twitter, meaning he was betting on a decline in the stock price, but it's unclear from Thursday's report if he still has that position. The firm didn't immediately respond to a request for comment. Citron warned that consumers are willing to boycott brands when they see issues of sexism and racism surface.

The Amnesty International report said that women of color were even more likely than white women to experience abuse on Twitter. According to the study, black and Asian women as well as Latinas and those of mixed race were 34 percent more likely to be mentioned in problematic or abusive tweets. Black women, in particular, were 84 percent more likely than white women to be mentioned, and abuse was directed at those across the political spectrum, the study said.

In response to the Amnesty report, Twitter Chief Legal Officer Vijaya Gadde said the following in a statement:

Twitter has publicly committed to improving the collective health, openness, and civility of public conversation on our service. Twitter's health is measured by how we help encourage more healthy debate, conversations, and critical thinking. Conversely, abuse, malicious automation, and manipulation detract from the health of Twitter. We are committed to holding ourselves publicly accountable towards progress in this regard.

Twitter pointed to the same statement when asked for comment about the Citron report.

Citron said Twitter should be facing the same level of criticism as Facebook, which has plunged of late and dropped again on Wednesday after The New York Times reported that the company had shared sensitive user data with big partners like Amazon and Spotify.

"As an investor, if you dislike Facebook you must absolutely HATE Twitter," Citron wrote.

Twitter shares fell $3.64 to $29.29 at Thursday's close.

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