Users of hook-up apps risk being blackmailed by hackers who have worked out how to exploit security flaws to steal users' data.

Security experts have issued a warning after three gay hookup apps and a threesome app were found to expose users' exact locations, just by knowing the publicly available username.

Any one of the 10 million worldwide users of Grindr, Romeo, Recon and 3Fun could be exposed - sparking fears that, if someone wanted to keep that aspect of their lives out of the public eye, they could be compromised.

Security experts have issued a warning after three gay hookup apps - including Grindr - and a threesome app were found to expose users' exact locations, just by knowing the publicly available username

A gay parliamentary staffer, who asked to be kept anonymous, said: 'The idea that every gay man who works for the government could be identified is terrifying.

'There are plenty of guys that would be fine, but those into fetishes might be very concerned they might get exposed.

'The only benefit I can see is finally putting a face to the topless torsos that keep messaging me every day.'

Researchers have already been able to find the locations of app users in the House of Commons, identifying them by tracking their home and work addresses.

Hookup apps Grindr and Romeo may also expose users in cities and countries where it is illegal to be gay, like Dubai and Saudi Arabia.

Recon, a gay kink and fetish app, could reveal their most private fantasies.

Alex Lomas, researcher at Pen Test Partners, said revealing members could also mean users could be victim of stalkers, exes and crime.

He said: 'In the UK, members of the BDSM community have lost their jobs if they happen to work in 'sensitive' professions like being doctors, teachers, or social workers.

'Being able to identify the physical location of LGBT+ people in countries with poor human rights records carries a high risk of arrest, detention, or even execution.'

3Fun - which is used to organise threesomes - was another app found to have security flaws

The firm created a tool that brings together information on the gay, kink and threesome apps, using fake locations to retrieve distances to user profiles from multiple points, pinpointing their location.

Security specialist Will Geddes said, 'If you have an app that discloses your location, you open yourself up to the possibility of extortion, physical harm, attack and anything across the spectrum of risk.'

He said homophobic governments could easily use the tool to track and arrest members of the LGBT community.

Mr Geddes likened it to being in a town square and shouting about your sexual preferences in the street.

He added: 'Sure, some people might want to have sex with you. But other people with malicious intent may use that information against you.'