Twitter Inc shares fell almost 7 percent after the company said it was investigating unusual traffic that it said might be from state-sponsored hackers.
In what appeared to be an unrelated issue, a security firm also said that hackers used the platform to try to steal user data.
Twitter said in a blog that it discovered suspicious traffic to a customer-support forum while investigating a security bug that exposed user data, including users' phone country codes and details on locked accounts. It said the bug was fixed on November 16.
Twitter said it observed a large amount of traffic to the customer support site coming from individual internet IP addresses in China and Saudi Arabia.
"During our investigation, we noticed some unusual activity involving the affected customer support form API. Specifically, we observed a large number of inquiries coming from individual IP addresses located in China and Saudi Arabia," Twitter said in a press release.
"While we cannot confirm intent or attribution for certain, it is possible that some of these IP addresses may have ties to state-sponsored actors," the blog said.
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