The leading UK site for parents has had users data compromised by hackers then using 'Heartbleed' exploit.
Mumsnet sent an email to users, warning that the hackers may have passwords and personal messages before network administrators were able to fix the vulnerability.
The website has urged all users to change their passwords.
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Marjorie and Michael Cawdery, both 83, are understood to have been stabbed to death in a killing their family called "incomprehensible".
Detectives have launched a murder investigation following the shooting in Brent, north west London on Friday night.
Hot and humid throughout the Bank Holiday Weekend.