Mr Giuliani, who served as the president's lawyer and also his cybersecurity advisor, suggested that Twitter had pulled a trick on him because they dislike Mr Trump.
But nothing of the sort happened, and Mr Giuliani actually appears to have tricked himself. Now he appears to be spreading conspiracy theories about Twitter in an attempt to deflect from that mistake.
The post came after Mr Giuliani accidentally posted a URL, while he was trying to write a normal sentence. While writing about the Mueller investigation, Mr Giuliani failed to hit the space bar and accidentally ran the words "G20.In" together, which turned them into a web address rather than just the end of a sentence and instead made it clickable.
When it became clear what had happened, one enterprising comedian bought up that G20.in URL and used it to host a website that simply said that Mr Trump is a traitor.
Now Mr Giuliani has seemed to suggest that he made no such mistake and that someone had "invaded" his post to share the link.
"Twitter allowed someone to invade my text with a disgusting anti-President message," the tweet read. "The same thing-period no space-occurred later and it didn’t happen. Don’t tell me they are not committed cardcarrying anti-Trumpers. Time Magazine also may fit that description. FAIRNESS PLEASE"
It is not quite clear what exactly Mr Giuliani meant by the tweet. But he appears to be suggesting that Twitter had allowed someone to exploit the service because it dislikes his boss.
In fact, however, anything that looks like a link and is posted on Twitter will appear that way. When Mr Giuliani tried other words to see if the same thing would happen again, it's possible that he used another word: it will only turn into a URL if the wording is a legitimate address, which happened in his first post because the .in domain is used in India.
Later in the same tweet, Mr Giuliani had written the words "Helsinki.Either", making the same mistake, and it could be that example that is pointing to. But website's addresses cannot end in ".either", meaning that Twitter's automated tools would not recognise it as a link.
Mr Giuliani was originally brought onto Mr Trump's team as his cybersecurity advisor.