Facebook Attachment Uploader Owned By A Space

Oh look – another vulnerability in Facebook! It wasn’t long ago we reported New Research Shows Facebook’s URL Scanner Is Vulnerable To Cloaking.

Well this time the private messaging function has been compromised, you can attach an executable and send it to anyone as long as you put a space after the filename.

It’s not the first time I’ve seen a mime/file/etc parser be owned by a space, but I expected better from Facebook to be honest.

A security penetration tester discovered a major flaw in Facebook that could allow a person to send anyone on the social-networking site malicious applications.

Nathan Power, a senior security penetration tester at technology consultancy CDW, discovered the vulnerability and publicly disclosed it Thursday on his blog. The flaw was reported to Facebook on Sept. 30, which acknowledged the issue on Wednesday, he wrote.

Power, who could not immediately be reached, wrote that Facebook does not normally allow a person to send an executable attachment using the “Message” tab. If you try to do that, it returns the message “Error Uploading: You cannot attach files of that type.”

Facebook has acknowledged the bug (which is a pretty serious one) but it’s unknown if they’ve actually fixed it yet or not.

You can see the original blog post outlining the vulnerability here:

Facebook Attach EXE Vulnerability

Good job Nathan Power!

Power wrote that an analysis of the browser’s “POST” request sent to Facebook’s servers showed that a variable called “filename” is parsed to see if a file should be allowed. But by simply by modifying the POST request with a space just after the file name, an executable could be attached to the message.

“This was enough to trick the parser and allow our executable file to be attached and sent in a message,” Power wrote.

A person would not have to be an approved friend of the sender, as Facebook allows people to send those who are not their friends messages. The danger is that a hacker could use social engineering techniques to coax someone to launched the attachment, which could potentially infect their computer with malicious software.

Facebook representatives contacted in London did not have an immediate response on Thursday afternoon.

The dangerous part I can see here is that Facebook allows users to send messages to anyone (with attachments) even if they are not friends. Which makes me wonder, how many random guys are sending girls they don’t know pictures of their junk as attachments on Faceobok messages…

I don’t want to know really.

Anyway this should be a fairly simple fix for Facebook and I’d imagine they have probably already fixed this or will be doing so fairly soon.

Source: Network World