Using: 
```wget -q -r https://csec.umd.edu/; grep -r -Poi UMDCTF-{.*?}```
shows us all the three flags from the CSEC Invasion challenges.
```csec.umd.edu/manifest.json:UMDCTF-{w3_d1d_th3_m@th}csec.umd.edu/robots.txt:UMDCTF-{d0m0_@r1g@t0_mr_r0b0t0}csec.umd.edu/index.html:UMDCTF-{@l13ns_@r3_b3tt3r_th@n_hum@ns}```