Recon, incertia edition

Challenge author
Will Song (SIGPwny)
Write-up author
chef (Batman's Kitchen)

I heard incertia made himself a super secret Instagram. Can you find it for me?

The first thing that we checked was Instagram, but there was no useful account with the name Incertia. With that we headed over to Twitter, where Incertia did have an account, @incertia. We found it odd that he tweeted about doorknobs right as the CTF started, so we knew that something must be up with that. Sadly, by going to Instagram and searching for doorknob accounts, we realized that there are strangely a lot of them. So back to Twitter again.

By searching through his account it is obvious that there is no Instagram link anywhere on there. From his pictures we can see that he has two of them with a girl @lucyclairejing. This account is linked to an Instagram and seems to be one of his good friends. Let's go back to Instagram, then, shall we?

We go to this girl's Instagram, which sadly also has no flag. This is the point that we remember the strange doorknob tweets from before. By using the search feature for the people who follow her, we see that there is a doorknob account called knobsondoors. The caption of the first picture on the account holds the flag flag{lik3_sh4d0ws_in_A_f4d3d_L1ghT_0h_we’re_inV1sib13}