david wong

Hey! I'm David, a security engineer at the Blockchain team of Facebook, previously a security consultant for the Cryptography Services of NCC Group. I'm also the author of the Real World Cryptography book. This is my blog about cryptography and security and other related topics that I find interesting.

[facebook bug bounty] Reading local files from facebook posted December 2014

Josip Franjković found a vulnerability in one of the file uploader of facebook.

He described what he did here

basically he uploaded a zipped file of a symbolic link to /etc/passwd

ln -s /etc/passwd link
zip --symlinks test.zip link

And since uploaders are always a mess to secure. Facebook just replied displaying the content of what he thought was the unzipped resume.

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