In January, 2016 the supermodel hosted a huge David Bowie themed bash at her home in Gloucestershire, England. The theme was chosen after the Ziggy Stardust musician died just days before Kate was due to celebrate her 42nd birthday.
Private photos of the event have now reportedly found their way online after a hacker obtained access to Lottie's social media account.
According to editors at Britain's The Sun newspaper, pictures showing Kate celebrating with on-off lover Count Nikolai von Bismarck were among those leaked by the hacker.
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Lottie, who is also a model, has reportedly become far more conscious about her cyber-security in the wake of the hack.
“Kate isn’t on social media but Lottie is quite open on all her platforms - although she has become far more guarded now," a source told the publication. “She realises she’s a target for trolls who want information on her and her sister.
“None of the images were ever intended to be shared with the world so it’s not very nice for them to have these personal moments pored over by some faceless hacker.”
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Revealing her Facebook had been compromised earlier this year, Lottie, 18, wrote, "When ur (sic) Facebook gets hacked and they change ur password lol (laugh out loud) okay.”
The aspiring model is not the only star with famous family members to have private pictures stolen in a cyber-attack.
Last Thursday a judge at Britain's High Court banned the publication of images allegedly stolen from the iCloud storage account of socialite Pippa Middleton.
The photographs are said to include family snaps of Pippa's royal sister Catherine, Duchess of Cambridge, her husband Prince William, the Duke of Cambridge, and their children, three-year-old Prince George and 17-month-old Princess Charlotte.
Representatives for Kate have yet to respond to requests for a comment.
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