https://cve.radiocsirt.org/rss/recent/all/10 Most recent entries from all 2026-10-07T05:12:37.653887+00:00 Vulnerability-Lookup csirt@opendfir.org python-feedgen Contains only the most 10 recent entries. https://cve.radiocsirt.org/vuln/euvd-2026-319056 EUVD-2026-319056 2026-10-07T05:12:37.700930+00:00 EUVD-2026-319056 https://cve.radiocsirt.org/vuln/fkie_cve-2026-42554 fkie_cve-2026-42554 2026-10-07T05:12:37.700969+00:00

Fiber is a web framework for Go. Prior to 2.52.12 and 3.1.0, Cross-Site Scripting vulnerability in Go Fiber allows a remote attacker to inject arbitrary HTML/JavaScript by supplying Accept: text/html on any request whose handler passes attacker-influenced data to the AutoFormat() feature. The developer opts into content negotiation by calling AutoFormat(), but does not opt into raw HTML emission for a particular request; Fiber chooses that branch from attacker-controlled Accept. The html branch is the sole outlier in a method whose name (AutoFormat) and symmetrical structure actively telegraph "safe, format-agnostic reply." This vulnerability is fixed in 2.52.12 and 3.1.0.

 https://cve.radiocsirt.org/vuln/ghsa-qjv7-627w-8qjv GHSA-qjv7-627w-8qjv — Fiber vulnerable to XSS in AutoFormat Content Negotiation 2026-10-07T05:12:37.701006+00:00

Affected: Go: github.com/gofiber/fiber/v3, Go: github.com/gofiber/fiber/v2

## Summary

**Description**

A Cross-Site Scripting (CWE-79) vulnerability in Go Fiber allows a remote attacker to inject arbitrary HTML/JavaScript by supplying `Accept: text/html` on any request whose handler passes attacker-influenced data to the AutoFormat() feature. This affects `github.com/gofiber/fiber/v3` (`DefaultRes.AutoFormat`) through version 3.1.0 and `github.com/gofiber/fiber/v2` (`Ctx.Format`) through version 2.52.12.

The developer opts into content negotiation by calling AutoFormat(), but does not opt into raw HTML emission for a particular request; Fiber chooses that branch from attacker-controlled Accept. Five of the six branches of the same method already escape. `JSON`, `XML`, `MsgPack`, and `CBOR` all route through encoders that neutralize markup; the txt branch emits `text/plain` and cannot execute. The html branch is the sole outlier in a method whose name (`AutoFormat`) and symmetrical structure actively telegraph "safe, format-agnostic reply."

## Details The issue resides in `res.go` within `(*DefaultRes).AutoFormat()`. The method negotiates against the request Accept header, selects one of `html | json | txt | xml | msgpack | cbor`, and serializes the caller-supplied body accordingly.

The "html" branch concatenates the stringified body directly into HTML markup with no output encoding: - `accept` comes from `r.c.Accepts(...)`, i.e. is fully attacker-controlled. An attacker can force the "html" branch on any `AutoFormat()` call regardless of which…