CVE-2026-25156 HotCRP vulnerable to stored XSS via comment attachments

High 7.3 Published 30 Jan 2026 Updated 2 Feb 2026

Attackers can execute arbitrary JavaScript in victims' browsers via malicious document uploads, potentially stealing credentials and accessing APIs.

Exploited in the wild: Not known
Login needed: Any signed-in user
Attackable: Over the internet
Victim action needed: A user has to click or open something
Fix: None listed

What is CVE-2026-25156?

CVE-2026-25156 is a high-severity cross-site scripting vulnerability in kohler hotcrp, published on 30 Jan 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

Official description

HotCRP is conference review software. HotCRP versions from October 2025 through January 2026 delivered documents of all types with inline Content-Disposition, causing them to be rendered in the user’s browser rather than downloaded. (The intended behavior was for only `text/plain`, `application/pdf`, `image/gif`, `image/jpeg`, and `image/png` to be delivered inline, though adding `save=0` to the document URL could request inline delivery for any document.) This made users who clicked a document link vulnerable to cross-site scripting attacks. An uploaded HTML or SVG document would run in the viewer’s browser with access to their HotCRP credentials, and Javascript in that document could eventually make arbitrary calls to HotCRP’s API. Malicious documents could be uploaded to submission fields with “file upload” or “attachment” type, or as attachments to comments. PDF upload fields were not vulnerable. A search of documents uploaded to hotcrp.com found no evidence of exploitation. The vulnerability was introduced in commit aa20ef288828b04550950cf67c831af8a525f508 (11 October 2025), present in development versions and v3.2, and fixed in commit 8933e86c9f384b356dc4c6e9e2814dee1074b323 and v3.2.1. Additionally, c3d88a7e18d52119c65df31c2cc994edd2beccc5 and v3.2.1 remove support for `save=0`.

Weakness: CWE-79

Which versions are affected by CVE-2026-25156?

It affects 1 product.

Products include Hotcrp Hotcrp.

How do I fix CVE-2026-25156?

No fix has been published for CVE-2026-25156 yet. Limit exposure of the affected software until one is available.

Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.

Is CVE-2026-25156 being exploited?

There is no known exploitation of CVE-2026-25156 in the wild and no public exploit code.

Sources

Also known as GHSA-p88p-2f2p-2476.