9001 copyparty up to 1.20.11 prologue.html cross site scripting

Summaryinfo

A vulnerability, which was classified as problematic, has been found in 9001 copyparty up to 1.20.11. The affected element is an unknown function of the file prologue.html. Performing a manipulation results in cross site scripting. This vulnerability is identified as CVE-2026-32109. The attack can be initiated remotely. There is not any exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic has been found in 9001 copyparty up to 1.20.11. This affects an unknown functionality of the file prologue.html. The manipulation with an unknown input leads to a cross site scripting vulnerability. CWE is classifying the issue as CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. This is going to have an impact on integrity. The summary by CVE is:

Copyparty is a portable file server. Prior to 1.20.12, if an attacker has been given both read- and write-permissions to the server, they can upload a malicious file with the filename .prologue.html and then craft a link to potentially execute arbitrary JavaScript in the victim's context. Note that it is intended behavior that the JavaScript would execute if the target clicks a link to the HTML file itself; "https://example.com/foo/.prologue.html". The vulnerability is that "https://example.com/foo/?b" would also evaluate the file, making the behavior unexpected. There are existing preventative measures (strict SameSite cookies) which makes it harder to leverage this vulnerability in an attack; in order to gain control of the target's authenticated session, the link must be clicked from a page served by the server itself -- most likely by editing an existing resource, which would require additional access permissions. Finally, for this attack to be successful, the attacker's target must click the specific crafted link given by the attacker. This vulnerability is not activated by normally browsing the web-UI on the server. This vulnerability is fixed in 1.20.12.

It is possible to read the advisory at github.com. This vulnerability is uniquely identified as CVE-2026-32109 since 03/10/2026. The exploitability is told to be difficult. It is possible to initiate the attack remotely. It demands that the victim is doing some kind of user interaction. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1059.007 according to MITRE ATT&CK.

By approaching the search of inurl:prologue.html it is possible to find vulnerable targets with Google Hacking.

Upgrading to version 1.20.12 eliminates this vulnerability.

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Productinfo

Vendor

• 9001

Name

• copyparty

Version

• 1.20.0
• 1.20.1
• 1.20.2
• 1.20.3
• 1.20.4
• 1.20.5
• 1.20.6
• 1.20.7
• 1.20.8
• 1.20.9
• 1.20.10
• 1.20.11

Website

• Product: https://github.com/9001/copyparty/

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