Twitter said Friday it has patched a bug that could have shared users' private messages with software developers outside of the company.

The issue is estimated to have impacted less than 1 percent of Twitter's total user base, which includes 335 million monthly active users as of July. The company has hundreds of partner developers.

The company's stock price hit a day low of $28.49 following the bug's disclosure. Twitter's share price closed at $28.50, down more than 4.5 percent on the day.

"We have no evidence to suggest that any data was improperly misused or exploited anywhere," a company spokeswoman told CNBC, emphasizing that the bug could only occur if a series of complex criteria were met. "There's virtually no possibility that this happened, but we still want to be thorough."

Twitter said it is continuing to investigate the situation. The company said it has also contacted third-party "developers who may have been impacted," the company said in a blog post.

The bug impacted user data between May 2017 and Sept. 10, when it was discovered. The bug was then fixed within hours, the Twitter spokeswoman said. The company waited to disclose the bug "to ensure we were providing the most accurate information," she said.

No private messages between individual users were shared with external software developers, the Twitter spokeswoman said.

Some users reacted to the bug disclosure by tweeting out the notice they received from the company.

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Here's Twitter's full statement: