Headline
CVE-2023-37467: SECURITY: Don't reuse CSP nonce between anonymous requests · discourse/discourse@0976c8f
Discourse is an open source discussion platform. Prior to version 3.1.0.beta7 of the beta and tests-passed branches, a CSP (Content Security Policy) nonce reuse vulnerability was discovered could allow cross-site scripting (XSS) attacks to bypass CSP protection for anonymous (i.e. unauthenticated) users. There are no known XSS vectors at the moment, but should one be discovered, this vulnerability would allow the XSS attack to bypass CSP and execute successfully. This vulnerability isn’t applicable to logged-in users. Version 3.1.0.beta7 contains a patch. The stable branch doesn’t have this vulnerability. A workaround to prevent the vulnerability is to disable Google Tag Manager, i.e., unset the gtm container id setting.
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@@ -637,36 +637,63 @@
it “when GTM is enabled it adds the same nonce to the policy and the GTM tag” do
SiteSetting.content_security_policy = true
SiteSetting.content_security_policy_report_only = true
SiteSetting.gtm_container_id = “GTM-ABCDEF”
get “/latest”
expect(response.headers).to include(“Content-Security-Policy”)
script_src = parse(response.headers[“Content-Security-Policy”])[“script-src”]
report_only_script_src =
parse(response.headers[“Content-Security-Policy-Report-Only”])[“script-src”]
nonce = extract_nonce_from_script_src(script_src)
report_only_nonce = extract_nonce_from_script_src(report_only_script_src)
expect(nonce).to eq(report_only_nonce)
gtm_meta_tag = Nokogiri::HTML5.fragment(response.body).css(“#data-google-tag-manager”).first
expect(gtm_meta_tag[“data-nonce”]).to eq(nonce)
end
it “doesn’t reuse CSP nonces between requests” do
it “doesn’t reuse nonces between requests” do
global_setting :anon_cache_store_threshold, 1
Middleware::AnonymousCache.enable_anon_cache
Middleware::AnonymousCache.clear_all_cache!
SiteSetting.content_security_policy = true
SiteSetting.content_security_policy_report_only = true
SiteSetting.gtm_container_id = “GTM-ABCDEF”
get “/latest”
expect(response.headers).to include(“Content-Security-Policy”)
expect(response.headers[“X-Discourse-Cached”]).to eq(“store”)
expect(response.headers).not_to include(“Discourse-GTM-Nonce-Placeholder”)
script_src = parse(response.headers[“Content-Security-Policy”])[“script-src”]
report_only_script_src =
parse(response.headers[“Content-Security-Policy-Report-Only”])[“script-src”]
first_nonce = extract_nonce_from_script_src(script_src)
first_report_only_nonce = extract_nonce_from_script_src(report_only_script_src)
expect(first_nonce).to eq(first_report_only_nonce)
gtm_meta_tag = Nokogiri::HTML5.fragment(response.body).css(“#data-google-tag-manager”).first
expect(gtm_meta_tag[“data-nonce”]).to eq(first_nonce)
get “/latest”
expect(response.headers).to include(“Content-Security-Policy”)
expect(response.headers[“X-Discourse-Cached”]).to eq(“true”)
expect(response.headers).not_to include(“Discourse-GTM-Nonce-Placeholder”)
script_src = parse(response.headers[“Content-Security-Policy”])[“script-src”]
report_only_script_src =
parse(response.headers[“Content-Security-Policy-Report-Only”])[“script-src”]
second_nonce = extract_nonce_from_script_src(script_src)
second_report_only_nonce = extract_nonce_from_script_src(report_only_script_src)
expect(second_nonce).to eq(second_report_only_nonce)
expect(first_nonce).not_to eq(second_nonce)
gtm_meta_tag = Nokogiri::HTML5.fragment(response.body).css(“#data-google-tag-manager”).first
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