Gnuboard g6 6.0.7 is vulnerable to Session hijacking due to a CORS misconfiguration.

Gnuboard 5.5.4 and 5.5.5 is vulnerable to Insecure Permissions. An attacker can change password of all users without knowing victim's original password.

A vulnerability was found in gnuboard5. It has been classified as problematic. Affected is an unknown function of the file bbs/faq.php of the component FAQ Key ID Handler. The manipulation of the argument fm_id leads to cross site scripting. It is possible to launch the attack remotely. Upgrading to version 5.5.8.2.1 is able to address this issue. The name of the patch is ba062ca5b62809106d5a2f7df942ffcb44ecb5a9. It is recommended to upgrade the affected component. The identifier of this vulnerability is VDB-213540.

Gnuboard 5.55 and 5.56 is vulnerable to Cross Site Scripting (XSS) via bbs/member_confirm.php.

Use of a Broken or Risky Cryptographic Algorithm in GitHub repository gnuboard/gnuboard5 prior to and including 5.5.5. A vulnerability in gnuboard v5.5.5 and below uses weak encryption algorithms leading to sensitive information exposure. This allows an attacker to derive the email address of any user, including when the 'Let others see my information.' box is ticked off. Or to send emails to any email address, with full control of its contents

gnuboard5 is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Cross Site Scripting (XSS) vulnerability in gnuboard5 <=v5.3.2.8 via the act parameter in bbs/move_update.php.

SQL Injection vulnerability in gnuboard5 <=v5.3.2.8 via the table_prefix parameter in install_db.php.

Cross Site Scripting (XSS) vulnerability in gnuboard5 <=v5.3.2.8 via the url parameter to bbs/login.php.

GNUBOARD5 5.3.1.9 has XSS that allows remote attackers to inject arbitrary web script or HTML via the "board tail contents" parameter, aka the adm/board_form_update.php bo_content_tail parameter.