So the original text from the executive order revokes the protection granted by by the privacy act

from the letter written by the ACLU;

The Act applies to any “system of records which is defined as “a group of any records under the control of any agency from which information is retrieved by the name of the individual or by some identifying number, symbol, or other identifying particular assigned to the individual.”

From my understanding after reading the article and their letter, they're claiming that this could potentially allow people who are not part of the government access to any information that is stored in the government databases, also government agencies that shouldn't have that info would have access so any info you wrote down on forms or whatever when applying for a green card for example can now be made easier to access by people, it would also allow them to collect info in cases where they previously could not.

It's not that it automatically causes issues but has the potential to cause issues.

the ACLU says it's unlikely to hold up to a legal challenge though and even if it were to be implemented there's a whole process it needs to go through before that.

that's all i know for now, not sure if it helped, i post a lot of these articles here to hear other people's explanations or additional facts about the matter, i hope someone else can explain it better.

I think their main fear is that that this EO is likely to be implemented in an unlawful way.