Personal information for some 3,191 congressional staffers has been leaked across the dark web, according to new research from internet security firm Proton being released Tuesday.

The firm said the data available in the hidden online hubs includes passwords, IP addresses and information from social media platforms.

“Many of these leaks likely occurred because staffers used their official email addresses to sign up for various services, including high-risk sites such as dating and adult websites, which were later compromised in data breaches,” Proton said in a statement. “This situation highlights a critical security lapse, where sensitive work-related emails became entangled with less secure, third-party platforms.”

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Proton, working with the firm Constella Intelligence, said it uncovered 1,848 passwords belonging to the political staffers available on the dark web, the digital underground frequented by hackers perusing difficult-to-find information.

The research showed one staffer alone had 31 passwords exposed online.

“The volume of exposed accounts among U.S. political staffers is alarming, and the potential consequences of compromised accounts could be severe,” said Eamonn Maguire, Proton head of account security, in a statement. “Vigilance and strict security measures are essential to safeguard personal and national security.”

The Switzerland-based Proton estimated that the information on nearly 1 in 5 congressional staffers is visible online. Nearly 300 staffers had their data exposed in more than 10 separate leaks.

Proton said it has reached out to all of the affected congressional staffers to alert them and the company said the exposed information were unrelated to Proton’s services that include products such as encrypted email accounts and password managers.

The company said it would share additional information about its findings on its blog this week, as the coming U.S. presidential election made the cybersecurity practices of influential staffers “more critical than ever.”

Congressional aides are not the only ones in hackers’ crosshairs: Google warned last month that the family and friends of political candidates and their campaigns need to brace for foreign hacking attempts.

“Vendors, in fact, often even the family or close friends of the candidate and possibly senior staff are often targeted by several of these attackers we talked about,” Google’s Sunny Consolvo said on a webinar in August. “And, so I think, it makes a lot of sense for people who are supporting campaigns — whether or not they’re officially part of the campaign or on the campaign’s Workspace — to make sure their settings are at the levels that are recommended for political campaigns as well.”

Google’s Threat Analysis Group revealed recently that it had stopped an Iranian hacking unit’s efforts aimed at breaching the campaigns of former President Donald Trump and President Biden in May and June.

The Biden administration said last week Mr. Biden’s campaign received unsolicited emails from Iranian cyberattackers containing stolen information from Mr. Trump’s campaign. An excerpt of the stolen detail appeared as text in the emails to Mr. Biden’s campaign, according to a statement from the Office of the Director of National Intelligence, the FBI and the Cybersecurity and Infrastructure Security Agency.

The federal agencies did not reveal precisely what was stolen, but sensitive research about Republican politicians was reportedly taken by Iranian hackers earlier this year and shared with media organizations.

Detail on Sen. Marco Rubio was reported to be included in the theft. Mr. Rubio, Florida Republican, told CBS on Sunday that he did not know what was stolen but doubted there was anything that could not be discovered by searching the internet.

Microsoft President Brad Smith told the Senate Select Committee on Intelligence last week that his company’s analysis of Iranian cyber operations revealed a “preference for a [Vice President Kamala] Harris victory.”

Russian operations, however, were inclined to denigrate the Democratic nominee, which Mr. Smith said in written testimony indicated support for Mr. Trump.