On the Facebook message, it shows the dates they allegedly slept together and the names of the couple’s kids.
Writing on Mumsnet, the baffled wife wrote: “I received a FB message a couple of days ago from someone who is claiming to have slept with my [husband].
“I’m pretty sure it’s nonsense, but I guess it’s niggling at me a little bit – she knows my name, named [husband] and our children., so I don’t think it’s mistaken identity.
“She’s given me four dates when they’re supposed to have been together.”
The mum went on to say that the four dates don’t add up, as three of them are “impossible”.
On one date the family were abroad, the other they were at a family wedding and the third was when the mum’s brother stayed round.
“I don’t know her, I’ve looked her up on Facebook but her profile is locked down,” the Mumsnetter explained.
“I don’t recognise her from her profile pic and we don’t seem to have any mutual friends.”
She added: “It’s mistaken identity or someone being weird, but at the same time the message is sitting in my inbox and every time I see it I do wonder.”
Many Mumsnetters flooded the parenting website with responses, with many confused about what could be going on.
One wrote: “Nothing is impossible. [There’s a] famous story of a man who took his mistress on holiday and installed her in the same hotel as his wife.”
Another said: “On the one hand she may be a malicious loon, on the other she may have got the dates wrong. I guess I’d ask her for more details.”
Other Mumsnetters thought the mum should trust her man as he’s given her no reason to doubt him.
One said: “Sounds weird, could be some scam/blackmail thing. Details such as kids names are very easy to find online, as scary as that is.”
But some women thought she should confront her husband to gauge his reaction, or tell the woman her dates don’t add up to see if she comes back with something “credible”