Oddly, many people have been left convinced by posts on certain UFO websites and YouTube channels that there may be some credit to the theory.
But, Express.co.uk can expose the latest claims, at least, as nothing more than a digitally-edited hoax.
Scott C Waring, who edits the popular ufosightingsdaily.com, has featured the black cubes on his website a number of times.
His latest post on them, published today featured claims he had found another one in an image taken by the the European space agency’s Solar and Heliospheric Observatory (SOHO), which he found online yesterday.
The images are then published by NASA.
The version of the image shown on Mr Waring’s website today, shows a black square, much bigger than earth in comparison to the sun, in the top left corner of the solar image.
Mr Waring posted a blog with the image entitled “Giant Borg Cube UFO Seen Orbiting Sun In NASA Photo”.
He wrote: “This sun photo is from the SOHO/NASA archive yesterday.
“You can see a cube-like craft moving between the sun and SOHO satellite.
“The edges of the craft are not pixelated, but instead looks like the silhouette of an alien spacecraft.
“These craft have been recorded for years and never explained by NASA.
“The craft are thought to be sucking a special energy from the sun, a type of energy that humanity has not learned about yet, but will in the future.”
We showed the post to UFO hoax buster Scott Brando.
He runs the website ufoofinterest.org, which debunks alleged UFO, alien and other paranormal sightings, following forensic analysis.
Mr Brando was able to quickly locate the original SOHO image, still available online, and appears to have busted Mr Waring in the process.
The image shows no black cube as seen on ufosightingsdaily.com.
Mr Brando said Mr Waring had “added a black square too give the appearance something was there that is not.”
Mr Brando said he had debunked earlier “sun black cube UFO” stories in the same way.
These included one which appeared on Mr Waring’s website last May.
At the time, Mr Waring’s blog gave the impression that NASA may have added the “black square” to conceal something behind it.
It sparked claims of a major UFO cover up by NASA among online conspiracy theorists.
But, Mr Brando, located the original image which featured only a very faint square shape, which he said was an “artefact anomaly”.
This is caused by things such as lens flare reflection, camera focus or pixelation during digital processing.
Mr Brando told Express.co.uk: “Someone painted a simple image artefact
“As I suspected it’s an image manipulated by Waring.
“It’s not the first time he did it.
“Waring coloured again that artefact in black to show something that in reality does not exist.
“It’s a hoax.”
Express.co.uk has contacted Mr Waring, and awaits a response.