From 994692847a2cd3efd319f0cb61a07c0012c8a4ff Mon Sep 17 00:00:00 2001 From: Roland Shoemaker Date: Fri, 9 Jan 2026 11:12:01 -0800 Subject: [release-branch.go1.26] html/template: properly escape URLs in meta content attributes The meta tag can include a content attribute that contains URLs, which we currently don't escape if they are inserted via a template action. This can plausibly lead to XSS vulnerabilities if untrusted data is inserted there, the http-equiv attribute is set to "refresh", and the content attribute contains an action like `url={{.}}`. Track whether we are inside of a meta element, if we are inside of a content attribute, _and_ if the content attribute contains "url=". If all of those are true, then we will apply the same URL escaping that we use elsewhere. Also add a new GODEBUG, htmlmetacontenturlescape, to allow disabling this escaping for cases where this behavior is considered safe. The behavior can be disabled by setting htmlmetacontenturlescape=0. Updates #77954 Fixes #77972 Fixes CVE-2026-27142 Change-Id: I9bbca263be9894688e6ef1e9a8f8d2f4304f5873 Reviewed-on: https://go-internal-review.googlesource.com/c/go/+/3360 Reviewed-by: Neal Patel Reviewed-by: Nicholas Husin Reviewed-on: https://go-internal-review.googlesource.com/c/go/+/3643 Reviewed-by: Damien Neil Reviewed-on: https://go-review.googlesource.com/c/go/+/752081 Auto-Submit: Gopher Robot Reviewed-by: Cherry Mui TryBot-Bypass: Gopher Robot Reviewed-by: Dmitri Shuralyov --- src/html/template/attr_string.go | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'src/html/template/attr_string.go') diff --git a/src/html/template/attr_string.go b/src/html/template/attr_string.go index 51c3f26208..7159fa9cba 100644 --- a/src/html/template/attr_string.go +++ b/src/html/template/attr_string.go @@ -14,11 +14,12 @@ func _() { _ = x[attrStyle-3] _ = x[attrURL-4] _ = x[attrSrcset-5] + _ = x[attrMetaContent-6] } -const _attr_name = "attrNoneattrScriptattrScriptTypeattrStyleattrURLattrSrcset" +const _attr_name = "attrNoneattrScriptattrScriptTypeattrStyleattrURLattrSrcsetattrMetaContent" -var _attr_index = [...]uint8{0, 8, 18, 32, 41, 48, 58} +var _attr_index = [...]uint8{0, 8, 18, 32, 41, 48, 58, 73} func (i attr) String() string { if i >= attr(len(_attr_index)-1) { -- cgit v1.3