Side A fixes a genuine XSS vulnerability by sanitizing untrusted Reddit HTML before rendering, adding a well-scoped module with tests and a clear security rationale. Side B fixes a real but narrower reducer bug (ghost items/pairs from zero-ratio votes) with a small, correct code move and updated test, which is valuable but lower-impact than closing an XSS hole.
constitution · epochs · watch · epoch 3
comparison
c_c0df72aee6da (tommy-mor) vs c_abd68b5e771a (tommy-mor)
download prompt · raw event · cmp_10eaf85f6ca5f4
council reasoning
A closes a real XSS hole by sanitizing untrusted Reddit HTML with ammonia at render time (shared helper, two call sites, unit tests), which is lasting security value. B is a precise, correct reducer bugfix (move zero-ratio return before ensure_item/voted_pairs) that prevents ghost state, but its scope and impact are narrower than preventing script execution in-origin.
Side A adds HTML sanitization with the `ammonia` library and routes all rendering of Reddit `body_html` through a shared `entity_body_html` function, preventing untrusted HTML (including scripts and event handlers) from executing while adding tests for benign and malicious input. Side B fixes an ordering bug by moving the zero-ratio early return before `ensure_item` and `voted_pairs.insert`, preventing ghost items and stale voted-pair state, but its impact is narrower than the cross-cutting XSS mitigation in Side A.
sides
A — c_c0df72aee6da (tommy-mor)
message
[bf118bdf] Sanitize Reddit entity body HTML before rendering. Use ammonia at render time so untrusted selftext_html cannot execute scripts in our origin. Co-authored-by: Cursor <cursoragent@cursor.com>
diff preview
diff --git a/Cargo.lock b/Cargo.lock
index 3dec7cb72a182dc654a37dca8ba0b49d77504daa..0dd4fce5fb6400ae153cca4e3dbf5a5158e6d8b4 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -11,6 +11,19 @@ dependencies = [
"memchr",
]
+[[package]]
+name = "ammonia"
+version = "4.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "17e913097e1a2124b46746c980134e8c954bc17a6a59bb3fde96f088d126dde6"
+dependencies = [
+ "cssparser",
+ "html5ever",
+ "maplit",
+ "tendril",
+ "url",
+]
+
[[package]]
name = "anyhow"
version = "1.0.102"
@@ -355,6 +368,29 @@ version = "0.2.4"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "460fbee9c2c2f33933d720630a6a0bac33ba7053db5344fac858d4b8952d77d5"
+[[package]]
+name = "cssparser"
+version = "0.35.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4e901edd733a1472f944a45116df3f846f54d37e67e68640ac8bb69689aca2aa"
+dependencies = [
+ "cssparser-macros",
+ "dtoa-short",
+ "itoa",
+ "phf",
+ "smallvec",
+]
+
+[[package]]
+name = "cssparser-macros"
+version = "0.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "13b588ba4ac1a99f7f2964d24b3d896ddc6bf847ee3855dbd4366f058cfcd331"
+dependencies = [
+ "quote",
+ "syn",
+]
+
[[package]]
name = "deranged"
version = "0.5.8"
@@ -381,6 +417,21 @@ version = "0.15.7"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "1aaf95b3e5c8f23aa320147307562d361db0ae0d51242340f558153b4eb2439b"
+[[package]]
+name = "dtoa"
+version = "1.0.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4c3cf4824e2d5f025c7b531afcb2325364084a16806f6d47fbc1f5fbd9960590"
+
+[[package]]
+name = "dtoa-short"
+version = "0.3.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cd1511a7b6a56299bd043a9c167a6d2bfb37bf84a6dfceaba651168adfb43c87"
+dependencies = [
+ "dtoa",
+]
+
[[package]]
name = "durable"
version = "0.2.0"
@@ -482,6 +533,16 @@ dependencies = [
"percent-encoding",
]
+[[package]]
+name = "futf"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "df420e2e84819663797d1ec6544b13c5be84629e7bb00dc960d6917db2987843"
+dependencies = [
+ "mac",
+ "new_debug_unreachable",
+]
+
[[package]]
name = "futures-channel"
version = "0.3.32"
@@ -614,6 +675,17 @@ version = "0.5.0"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "2304e00983f87ffb38b55b444b5e3b60a884b5d30c0fca7d82fe33449bbe55ea"
+[[package]]
+name = "html5ever"
+version = "0.35.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "55d958c2f74b664487a2035fe1dadb032c48718a03b63f3ab0b8537db8549ed4"
+dependencies = [
+ "log",
+ "markup5ever",
+ "match_token",
+]
+
[[package]]
name = "http"
version = "1.4.1"
@@ -974,6 +1046,15 @@ version = "0.8.2"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "92daf443525c4cce67b150400bc2316076100ce0b3686209eb8cf3c31612e6f0"
+[[package]]
+name = "lock_api"
+version = "0.4.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "224399e74b87b5f3557511d98dff8b14089b3dadafcab6bb93eab67d3aace965"
+dependencies = [
+ "scopeguard",
+]
+
[[package]]
name = "log"
version = "0.4.30"
@@ -990,6 +1071,40 @@ dependencies = [
"libc",
]
+[[package]]
+name = "mac"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c41e0c4fef86961ac6d6f8a82609f55f31b05e4fce149ac5710e439df7619ba4"
+
+[[package]]
+name = "maplit"
+version = "1.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3e2e65a1a2e43cfcb47a895c4c8b10d1f4a61097f9f254f183aee60cad9c651d"
+
+[[package]]
+name = "markup5ever"
+version = "0.35.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "311fe69c934650f8f19652b3946075f0fc41ad8757dbb68f1ca14e7900ecc1c3"
+dependencies = [
+ "log",
+ "tendril",
+ "web_atoms",
+]
+
+[[package]]
+name = "match_token"
+version = "0.35.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ac84fd3f360fcc43dc5f5d186f02a94192761a080e8bc58621ad4d12296a58cf"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
[[package]]
name = "matchers"
version = "0.2.0"
@@ -1092,6 +1207,12 @@ dependencies = [
"tempfile",
]
+[[package]]
+name = "new_debug_unreachable"
+version = "1.0.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "650eef8c711430f1a879fdd01d4745a7deea475becfb90269c06775983bbf086"
+
[[package]]
name = "nom"
version = "7.1.3"
@@ -1175,6 +1296,29 @@ dependencies = [
"vcpkg",
]
+[[package]]
+name = "parking_lot"
+version = "0.12.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "93857453250e3077bd71ff98b6a65ea6621a19bb0f559a85248955ac12c45a1a"
+dependencies = [
+ "lock_api",
+ "parking_lot_core",
+]
+
+[[package]]
+name = "parking_lot_core"
+version = "0.9.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2621685985a2ebf1c516881c026032ac7deafcda1a2c9b7850dc81e3dfcb64c1"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "redox_syscall",
+ "smallvec",
+ "windows-link",
+]
+
[[package]]
name = "peeking_take_while"
version = "0.1.2"
@@ -1187,6 +1331,58 @@ version = "2.3.2"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "9b4f627cb1b25917193a259e49bdad08f671f8d9708acfd5fe0a8c1455d87220"
+[[package]]
+name = "phf"
+version = "0.11.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1fd6780a80ae0c52cc120a26a1a42c1ae51b247a253e4e06113d23d2c2edd078"
+dependencies = [
+ "phf_macros",
+ "phf_shared",
+]
+
+[[package]]
+name = "phf_codegen"
+version = "0.11.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "aef8048c789fa5e851558d709946d6d79a8ff88c0440c587967f8e94bfb1216a"
+dependencies = [
+ "phf_generator",
+ "phf_shared",
+]
+
+[[package]]
+name = "phf_generator"
+version = "0.11.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3c80231409c20246a13fddb31776fb942c38553c51e871f8cbd687a4cfb5843d"
+dependencies = [
+ "phf_shared",
+ "rand 0.8.6",
+]
+
+[[package]]
+name = "phf_macros"
+version = "0.11.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f84ac04429c13a7ff43785d75ad27569f2951ce0ffd30a3321230db2fc727216"
+dependencies = [
+ "phf_generator",
+ "phf_shared",
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "phf_shared"
+version = "0.11.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "67eabc2ef2a60eb7faa00097bd1ffdb5bd28e62bf39990626a582201b7a754e5"
+dependencies = [
+ "siphasher",
+]
+
[[package]]
name = "pin-project-lite"
version = "0.2.17"
@@ -1223,6 +1419,12 @@ dependencies = [
"zerocopy",
]
+[[package]]
+name = "precomputed-hash"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "925383efa346730478fb4838dbe9137d2a47675ad789c546d150a6e1dd4ab31c"
+
[[package]]
name = "prettyplease"
version = "0.2.37"
@@ -1379,6 +1581,15 @@ dependencies = [
"rand_core 0.9.5",
]
+[[package]]
+name = "redox_syscall"
+version = "0.5.18"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ed2bf2547551a7053d6fdfafda3f938979645c44812fbfcda098faae3f1a362d"
+dependencies = [
+ "bitflags 2.11.1",
+]
+
[[package]]
name = "regex"
version = "1.12.3"
@@ -1563,6 +1774,12 @@ dependencies = [
"windows-sys 0.61.2",
]
+[[package]]
+name = "scopeguard"
+version = "1.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "94143f37725109f92c262ed2cf5e59bce7498c01bcc1502d7b9afe439a4e9f49"
+
[[package]]
name = "security-framework"
version = "3.7.0"
@@ -1683,6 +1900,12 @@ dependencies = [
"libc",
]
+[[package]]
+name = "siphasher"
+version = "1.0.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8ee5873ec9cce0195efcb7a4e9507a04cd49aec9c83d0389df45b1ef7ba2e649"
+
[[package]]
name = "slab"
version = "0.4.12"
@@ -1709,6 +1932,7 @@ dependencies = [
name = "sorter2-server"
version = "0.0.1"
dependencies = [
+ "ammonia",
"async-stream",
"axum",
"axum-extra",
@@ -1742,6 +1966,31 @@ version = "1.2.1"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "6ce2be8dc25455e1f91df71bfa12ad37d7af1092ae736f3a6cd0e37bc7810596"
+[[package]]
+name = "string_cache"
+version = "0.8.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bf776ba3fa74f83bf4b63c3dcbbf82173db2632ed8452cb2d891d33f459de70f"
+dependencies = [
+ "new_debug_unreachable",
+ "parking_lot",
+ "phf_shared",
+ "precomputed-hash",
+ "serde",
+]
+
+[[package]]
+name = "string_cache_codegen"
+version = "0.5.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c711928715f1fe0fe509c53b43e993a9a557babc2d0a3567d0a3006f1ac931a0"
+dependencies = [
+ "phf_generator",
+ "phf_shared",
+ "proc-macro2",
+ "quote",
+]
+
[[package]]
name = "subtle"
version = "2.6.1"
@@ -1813,6 +2062,17 @@ dependencies = [
"windows-sys 0.61.2",
]
+[[package]]
+name = "tendril"
+version = "0.4.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d24a120c5fc464a3458240ee02c299ebcb9d67b5249c8848b09d639dca8d7bb0"
+dependencies = [
+ "futf",
+ "mac",
+ "utf-8",
+]
+
[[package]]
name = "thiserror"
version = "1.0.69"
@@ -2116,6 +2376,12 @@ version = "2.1.3"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "daf8dba3b7eb870caf1ddeed7bc9d2a049f3cfdfae7cb521b087cc33ae4c49da"
+[[package]]
+name = "utf-8"
+version = "0.7.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "09cc8ee72d2a9becf2f2febe0205bbed8fc6615b7cb429ad062dc7b7ddd036a9"
+
[[package]]
name = "utf8_iter"
version = "1.0.4"
@@ -2281,6 +2547,18 @@ dependencies = [
"wasm-bindgen",
]
+[[package]]
+name = "web_atoms"
+version = "0.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "57ffde1dc01240bdf9992e3205668b235e59421fd085e8a317ed98da0178d414"
+dependencies = [
+ "phf",
+ "phf_codegen",
+ "string_cache",
+ "string_cache_codegen",
+]
+
[[package]]
name = "windows-link"
version = "0.2.1"
diff --git a/server/Cargo.toml b/server/Cargo.toml
index 47659ff82fbfb50972eb2b87575e80f66e572ba4..27f552c20b97ef28cdde4cb6b1a4980375135111 100644
--- a/server/Cargo.toml
+++ b/server/Cargo.toml
@@ -13,6 +13,7 @@ serde = { version = "1", features = ["derive"] }
serde_json = "1"
thiserror = "1"
maud = { version = "0.26", features = ["axum"] }
+ammonia = "4.1"
tower = "0.5"
tower-http = { version = "0.5", features = ["trace"] }
tracing = "0.1"
diff --git a/server/src/fetch/html.rs b/server/src/fetch/html.rs
index dadf050515f0473943dad97df5d318032c8cb385..5b160c6b8bd216dfaf80149854aec0566cd00460 100644
--- a/server/src/fetch/html.rs
+++ b/server/src/fetch/html.rs
@@ -4,6 +4,7 @@ use maud::{html, Markup};
use crate::{
form_template::template_json_compact,
+ html::sanitize::entity_body_html,
path_types::ItemId,
reddit::{is_children_fetchable, is_fetchable},
reducer::NodeState,
@@ -27,7 +28,7 @@ pub fn entity_panel(node: &NodeState) -> Markup {
p class="muted small" { "by " (author) }
}
@if let Some(body) = &data.body_html {
- div class="entity-body" { (maud::PreEscaped(body)) }
+ div class="entity-body" { (maud::PreEscaped(entity_body_html(body))) }
}
}
}
diff --git a/server/src/html/mod.rs b/server/src/html/mod.rs
index e180a0ca542a33e2300c0a4809e6b9cfee07ecfe..a58cbbee3490a08a625cb06df06848c59a615d65 100644
--- a/server/src/html/mod.rs
+++ b/server/src/html/mod.rs
@@ -20,6 +20,7 @@ use crate::{
ui
… preview truncated; 2,223 characters omittedB — c_abd68b5e771a (tommy-mor)
message
[81de487b] Fix zero-ratio guard in reducer to drop before registering items or pair. Previously the early-return for zero-weight votes happened after ensure_item and voted_pairs.insert, leaving ghost items in the index and the pair incorrectly marked as voted. Move the check to before any side effects. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
diff preview
diff --git a/server/src/reducer.rs b/server/src/reducer.rs
index 6841d35cfc9de2389f340a22b8a45acb335e36c3..0e36979abe0f051493038ff7e652efc7f7a0ac80 100644
--- a/server/src/reducer.rs
+++ b/server/src/reducer.rs
@@ -112,6 +112,10 @@ impl GroupState {
if vote.ratio_right < 0 {
vote.ratio_right = 0;
}
+ if vote.ratio_left == 0 || vote.ratio_right == 0 {
+ // Zero on either side produces no valid edge; drop before registering items or pair.
+ return;
+ }
let a_idx = self.ensure_item(&vote.a);
let b_idx = self.ensure_item(&vote.b);
@@ -121,10 +125,6 @@ impl GroupState {
let w_a = vote.ratio_left as f64;
let w_b = vote.ratio_right as f64;
- if w_a == 0.0 || w_b == 0.0 {
- // Zero on either side produces no valid edge; drop the vote.
- return;
- }
self.add_edge_weight(b_idx, a_idx, w_a);
self.add_edge_weight(a_idx, b_idx, w_b);
diff --git a/server/tests/basic.rs b/server/tests/basic.rs
index cc8c1a0d139f3722ba6ecd13dd001c65be835b67..08159f4a7f0850fd165817a4a1af4f31ced2ad76 100644
--- a/server/tests/basic.rs
+++ b/server/tests/basic.rs
@@ -546,12 +546,10 @@ fn reducer_negative_ratio_clamped_to_zero() {
delegate: Some("00000000-0000-0000-0000-000000000000:test:local/test".to_string()),
thread_tag: "t".to_string(),
});
- // Items are registered, but the zero-clamped vote produces no edges.
- assert_eq!(group.idx_to_item.len(), 2);
- let a_idx = group.item_to_idx[&item_id("https://slug.social/~/t/a")];
- let b_idx = group.item_to_idx[&item_id("https://slug.social/~/t/b")];
- assert!(!group.edges.contains_key(&(a_idx, b_idx)));
- assert!(!group.edges.contains_key(&(b_idx, a_idx)));
+ // Nothing registered: zero-clamped vote is dropped before ensure_item.
+ assert!(group.idx_to_item.is_empty());
+ assert!(group.edges.is_empty());
+ assert!(group.voted_pairs.is_empty());
}
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