Okay, so straight off the bat I really don't like the sheer amount of [DATA EXPUNGED] used. I'm personally against using it at all, I think it interrupts the flow and breaks suspension of disbelief. The only acceptable time to use it is if it's information that the Foundation considers too potentially dangerous to be left in the report. Going through each of them in turn:

SCP-XXXX is a sentient mass of liquid, composed of approximately one part [DATA EXPUNGED] to one part unknown biological substance.

This simply isn't detailed enough for a scientific report. Given its eating habits, you could say it's composed of water with extremely high calcium content, or take a look at this article on bone marrow and use details from here as the 'unknown biological substance'.

Currently, the only known materials it cannot adhere to are [DATA EXPUNGED]

Why does the Foundation consider this need-to-know information? If there's a material it can't adhere to, then surely they should make the containment cell from it.

… and consumes the bones of the subject. This process takes [DATA EXPUNGED], and causes immediate cardiac arrest.

If it's been observed, then researchers should have an idea of how long it takes. I don't think this needs to be redacted for any reason.

The fastest speed it has ever moved at is approximately ███ m/s.

Black-box rather than redaction, but even so - if you don't want to state the speed of movement, does this detail need to be included? All it tells the reader is: 'It can move fast'.

SCP-XXXX has never attacked any living creatures that are not human, but will [DATA EXPUNGED].

Will what? Tenderly make out with it? Make a business proposition? Deliver a monologue on the systemic issues plaguing Western-style democratic governments and how they've enabled the right of extremist politics and convenient political scape-goating?

I assume you want to imply 'something awful happens' but you've cut away too much of the surrounding sentence, which means I, the reader, have no frame of reference to guide my imagination.

and attempts from an amputee to touch it resulted in [DATA EXPUNGED]

Was whatever happened any worse than it sliding under your nails and eating your skeleton? If not, just include it.

It does, however, grow agitated when not fed, and after ██ days without food it ███████ the next personnel who entered the room, but did not consume them.

If that's the case why doesn't the Foundation just lock it in a room and throw bones at it occasionally through a secure hatch?

Containment Procedures

The description doesn't indicate to me the necessity of keeping a D-Class permanent resident in with the worm-thing. From what you've described it does seem like you could lock it in a box and just feed it occasionally like some kind of exotic, skeleton-devouring sea slug. Also why does the D-Class have to use a bucket? Is this simply to avoid the SCP jumping down the toilet and entering the sewers? And why specifically a rabbit skeleton? The test log has the researchers using chicken bones to no apparent ill effect.

Description

It appears to slither like a snake when it moves

If it slithers, then it is slithering, rather than appearing to.

SCP-XXXX, upon gaining line of sight of a human's finger or toe nails,

This will happen even when the subject's hands and feet are covered with protective equipment

So why does wax stop it? If my hands are covered by gloves, then SCP-XXXX can't see my fingernails (also how does it see or sense anything, judging by the picture it's a weird mass of milky-white tendrils).

I'm also left wondering how this thing survived before it was located - you admittedly say it doesn't starve to death, but then why does it eat human skeletons to begin with? It might be worth thinking out an origin story for this thing, how did the Foundation find it? Are there other instances of this species around?

Other Issues with Content

Prior to Test XXXX-III

Don't use Roman numerals. Just call the test logs 'SCP-XXXX-1', etc.

On the image, you don't necessarily need to include 'underwater, where it was found'. That can be implied just from the image itself.