It's looking like today's stock market session is on track to deliver investors another gain. At the time of writing, the S&P/ASX 200 Index (ASX: XJO) has risen by a rosy 0.45%, pulling the index back over 7,100 points. But one ASX 200 stock – in fact, an ASX 100 stock – is going the other way today.

Cleanaway Waste Management Ltd (ASX: CWY) is the ASX 100 stock in question. And it's seemingly having an awful day.

Cleanaway shares closed at $3.01 each yesterday. But this morning, the waste management company opened at just $2.60 and is currently trading at $2.67 a share, down a nasty 11.3% for the day thus far.

So why is this ASX 100 stock so clearly bucking the market and having such a miserable session this Wednesday?

What's up with the Cleanaway stock price?

Well, to answer that, we need a little more context. So sure, this fall that Cleanaway shares are experiencing today looks dramatic. But it follows an even more unusual move we saw happen yesterday.

Yesterday was a relatively calm day for this ASX 100 stock. At least it was, until a few minutes before market close. These few minutes unexpectedly saw Cleanaway shares rocket around 15% up to a new 52-week high of $3.01, which is where the stock closed at yesterday afternoon.

This morning's plunge just took some of the steam out of yesterday's late pricing surge. Cleanaway shares remain comfortably above where they started the day yesterday.

Well, some ASX releases put out by Cleanaway shed some light on this rather bizarre situation.

The ASX 100 stock received an ASX speeding ticket yesterday evening for the shenanigans of its share price in the afternoon. In its query, the ASX noted the "change in the price of CWY's securities from $2.65 at 4PM to $3.01 at the completion of the closing auction today".

In its response this morning, Cleanaway blamed the spike on "media speculation regarding a possible takeover offer by Seven Group Holdings Limited".

Seven Group Holdings Ltd (ASX: SVW) is the conglomerate behind several other businesses, including oil and gas, media and heavy equipment.

According to several media outlets, including Bloomberg, Seven "has been seeking financing for a potential takeover of Melbourne-based Cleanaway Waste".

Seven has been silent on this whole affair so far. However, Cleanaway released a supplementary ASX filing this morning, which stated the following:

Cleanaway confirms that it is not in any discussions with SGH in relation to any form of corporate transaction or otherwise, nor has it received an approach or offer from SGH.

So given Cleanaway shares' reluctance to go back to where they were before yesterday's spike today, it looks as though investors remain hopeful that there's something here.

But for now, at least, it looks as though this rather strange chapter in Cleanaway's share price history has closed.