As far as anyone can tell, it's BS.  It's been asked in the #monero-dev channel and no one is aware of anything.  If I had to make my own guess, someone sent a forged email to a bunch of exchanges... some of them took the bait.

Here's a transcript from IRC earlier today.  Times in US-Eastern:


11:19 AM <@fluffypony> ghpg: there's no special email list, there's the announce list that you can join
11:20 AM <@fluffypony> I have no idea why a block explorer would be down
11:20 AM <@fluffypony> we're pretty close to tagging 0.13
11:20 AM <+moneromooo> gingeropolous said he tried to pop blocks on a running monerod, and the importer started a format conersion -> hosed.
11:20 AM w00t
11:20 AM woohoo!
11:20 AM fluffypony: this one https://lists.getmonero.org/hyperkitty/list/monero-announce@lists.getmonero.org/2018/7/ ? it has no history for july and I guess you (monero) contacted exchanges about the duplicate count bug?
11:21 AM <@fluffypony> yes that one
11:21 AM <+moneromooo> hyperkitty... now that's a software I wanna use.
11:21 AM <@fluffypony> lol
11:21 AM ⇐ xnbya quit  •  moneromooo → +hyperkitty 
11:21 AM <@fluffypony> ghpg: occasionally if there's something super sensitive we might just directly email list subscribers
11:23 AM to clear it up, are the wallets down on most exchanges due to a bug similar to the last double count bug? too many threads on reddit without a clear answer on that
11:23 AM <+hyperkitty> You'll find out if you subscribe to... hyperkitty!
11:24 AM <@fluffypony> camthegeek: Bitfinex and Kraken look just fine
11:24 AM camthegeek AFAIK no one knows
11:24 AM Its not due to a bug/issue
11:24 AM at least not one known by anyone here AFAIK
11:25 AM ok, thank you
11:25 AM well then, someone has stirred the pot of BS.
11:25 AM Yeah
11:25 AM r/monero feels heavily brigaded lately
11:25 AM hyperkitty, love the name. I'd support it.
11:25 AM it is.
11:25 AM Lots of accounts I've never seen, spamming about wallet issues/the latest "bug"
11:25 AM That all sprang up at the same time
11:25 AM I've drifted away from it lately. too much crap :|
11:25 AM → +hyc (voiced) joined 
11:25 AM Its normally not too bad
11:25 AM But this last week has been rough
11:25 AM Idk why
11:26 AM But we should take that convo elsewhere
11:26 AM Don't think any of the devs here know whats going on with the exchange wallets, and no exchange has posted about why
11:26 AM So for now... 🤷
11:27 AM → dog\ joined (~dog@gateway/tor-sasl/dog/x-12068491)
11:28 AM but as fluffypony said, the larger volume exchanges are still kickin' just fine. I'll poke around with support emails and try to see whats up :p
11:28 AM → xnbya joined (~quassel@ec2-54-72-128-94.eu-west-1.compute.amazonaws.com)
11:28 AM Yeah its nothing to worry about I dont think
11:28 AM Just a coincidence that people are panicking over
11:33 AM → orbit33, cardboardoranges, p0nziph0ne and coppa joined 
11:41 AM Well, on cryptopia the status reads "24-SEP-2018 - XMR Wallet placed in maintenance at the request of the Coin Developer."  .. Maybe it's a bug the devs aren't willing to talk about before it's fixed
11:42 AM → ndorf joined (~nd@ob.noxio.us)
11:42 AM Don't know why no core dev would mention it though
11:43 AM They could announce there is a bug they are fixing etc, without announcing details
11:43 AM Yeah, strange :/
11:43 AM Could just be Cryptopia BSing
11:43 AM But Idk
11:43 AM Not sure if moneromooo or others want to comment on any of it
11:44 AM Think its all just brigading/trolls tbh
11:44 AM Which aren't worth devs time
11:44 AM I suspect it's actually another CN-coin
11:44 AM kraken is fine, bithumb is fine, hitbtc is fine, binance is fine
11:44 AM Thats the more probably solution, if there is a CN issue
11:45 AM An old, patched exploit some fork didn't account for maybe
11:45 AM <@fluffypony> we're busy with the 0.13 release candidate, which is very very close
11:45 AM <@fluffypony> so don't really have time to deal with it
11:45 AM I don't know, but it's def weird... as said before, to me kraken is (together with bitstamp) the most trustworthy exchange
11:45 AM Understandable fluffypony
11:46 AM they would def know if something was up, and they would certainly not take any risk
11:46 AM And thats exciting
11:46 AM Yeah thats why I don't think its anything of importance orbit33
11:46 AM vegasbaby When I look at other CN coins on cryptopia many of them are in maintenance mode as of 24 sep. 2018 with the note "at the request of the coin developer" so you're probably right their message is bullshit
11:46 AM and indeed, probably devs have other things on their mind
11:46 AM Mibka ah nice find
11:46 AM than explaining why some exchange freezes xmr if they don't actually know why