Dozens of articles are coming about about a guy who was able to identify the wallet address origins of 96% of the transactions on the grin blockchain by running a node on the network ($60/month).
https://www.ccn.com/litecoin-creator-charlie-lee-responds-to-mimblewimble-privacy-vulnerability/
This limitation of MimbleWimble protocol is well known. MW is basically Confidential Transactions with scaling benefits and slight unlinkablility. To get much better privacy, you can still use CoinJoin before broadcasting and CJ works really well with MW due to CT and aggregation.
---Charlie Lee (Litecoin founder)
Eh, well that's news to me. Weird how everyone markets MimbleWimble as superior privacy tech that doesn't actually do what is advertised. I thought obscuring the addresses was the entire point of it.
In any case these things take time. Perhaps this "fatal flaw" will get patched or mitigated sometime in the future.
Conclusion
This certainly comes at a weird time when the Grin dev team just got a 50 BTC donation from a wallet that hasn't exchanged hands since 2011. Maybe they'll put that money to good use.