## Rev/sl4ydroid (55 solves)Created by: `Sl4y3r_07`
> This challenge has got some Rizz !!
The app (on startup) displays this.
![Initial Display](https://seall.dev/images/ctfs/backdoorctf2023/sl4ydroid_1.png)
I opened the apk with jadx and had a look through the functions on `MainActivity` and noticed this particular portion.
```javapublic void onCreate(Bundle savedInstanceState) {	super.onCreate(savedInstanceState);	setContentView(C0567R.layout.activity_main);	TextView textView = (TextView) findViewById(C0567R.C0570id.displayTextView);	this.displayTextView = textView;	textView.setVisibility(8);	TextView textView2 = (TextView) findViewById(C0567R.C0570id.textView);	this.textView = textView2;	textView2.setText(getResources().getString(C0567R.string.message));	kim(getResources().getString(C0567R.string.f116k1));	nim(getResources().getString(C0567R.string.f117n1));	damn(getResources().getString(C0567R.string.f115d1));	m105k2(getResources().getString(C0567R.string.k21));}```
The app shows some text normally, and we can see some texts visibility being edited and some text being shown.
I connect my phone and prepare an ADB bridge with jadx. Looking through the Smali I put a breakpoint at:
 - line 225 (`invoke-virtual      {v0, v1}, Landroid/widget/TextView;->setVisibility(I)V`) - line 238 (`invoke-virtual      {v0, v1}, Landroid/widget/TextView;->setText(Ljava/lang/CharSequence;)V`)
On the first breakpoint shows setting the visibility. We change this (`v1`) to `0` to make it visible.
![Visibility Change Only](https://seall.dev/images/ctfs/backdoorctf2023/sl4ydroid_2.png)
On the second breakpoint we change this (`v1`) from `Flag will not display here.` to ` ` (a space), to make it invisible.
![Visibility Change + Removal of text](https://seall.dev/images/ctfs/backdoorctf2023/sl4ydroid_3.png)
Continuing past the breakpoints were shown our flag: `flag{RizZZ! Rc4_R3v3r51Ngg_RrR!:}`.
**Files:** [slaydroid.zip](https://web.archive.org/web/20231218160004/https://staticbckdr.infoseciitr.in/slaydroid.zip)