File upload - Limited file uploads

Good morning.

I seek help. I’ve been trying to get the XXE running for two days now.

I took the code, created a vim file called pic.svg and pasted it in there:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE svg [ <!ENTITY xxe SYSTEM "file:///etc/passwd"> ]>
<svg>&xxe;</svg>

Unfortunately, when I run it, I receive the following error:

“This XML file does not appear to have any style information associated with it. The document tree is shown below.”

Has it the wrong format? Do I have to do stuff in Burp?

Edit: It worked. I had to show the source code of the image and not go into the directory.

I found this on Hacktricks and tried it:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE foo [<!ENTITY example SYSTEM "file:///etc/passwd"> ]>
<data>&example;</data>

why does this code not work?

it does not work because there is no /etc/flag.txt , the flag.txt file is in the root directory. You need to fix your file path.

yesh, filepath issue,
give LongPath Tool Program to good effect to use and manipulate, good good.