If you have a file with @ sign at end, this is how to remove extended attributes on the Mac OS.

Example.

ls -l
-rwxr-xr-x@  4 username  staff   128 Mar 24 10:51 sample.txt

Remove extended attributes.

xattr -c sample.txt

Result

ls -l
-rwxr-xr-x  4 username  staff   128 Mar 24 10:51 sample.txt