diff --git a/docs/CONFIG.md b/docs/CONFIG.md
index 7155457..c9ed36d 100644
--- a/docs/CONFIG.md
+++ b/docs/CONFIG.md
@@ -55,6 +55,17 @@ omitted to keep the file minimal. Scan-target inputs (paths, `--git-url`,
 GitHub/GitLab/etc. flags, S3/GCS buckets) are stripped — they describe
 *what* this run scans and don't belong in shared project policy.
 
+## Webhook URL policy
+
+`alerts.webhooks[].url` (and `--alert-webhook URL`) **must use `https://`**.
+Webhook URLs typically embed a secret token in the path and the alert
+payload contains finding metadata, so cleartext transport is never the right
+default. `http://` is allowed only when the host is a loopback address
+(`localhost`, `127.0.0.0/8`, `::1`) — useful for local development against an
+on-host receiver. Loopback decisions are made on the literal hostname / IP
+in the URL; we do not consult DNS, so a resolver cannot trick the validator
+into permitting `http://` for a remote host.
+
 ## Caveats
 
 - **`scan.jobs` and the Tokio runtime.** The Tokio runtime is sized from the
diff --git a/src/alerts/discord.rs b/src/alerts/discord.rs
index 8066e09..58598a5 100644
--- a/src/alerts/discord.rs
+++ b/src/alerts/discord.rs
@@ -56,13 +56,16 @@ pub fn build_payload(
     if let Some(t) = &summary.target {
         fields.push(json!({
             "name": "Target",
-            "value": format!("`{}`", truncate(t, 1000)),
+            "value": format!("`{}`", escape_for_code_span(&truncate(t, 1000))),
             "inline": false,
         }));
     }
     if !summary.by_rule.is_empty() {
-        let lines: Vec<String> =
-            summary.by_rule.iter().map(|(rule, count)| format!("• `{rule}` — {count}")).collect();
+        let lines: Vec<String> = summary
+            .by_rule
+            .iter()
+            .map(|(rule, count)| format!("• `{}` — {count}", escape_for_code_span(rule)))
+            .collect();
         fields.push(json!({
             "name": "Top rules",
             "value": truncate(&lines.join("\n"), 1000),
diff --git a/src/alerts/mattermost.rs b/src/alerts/mattermost.rs
index a2b6582..dda633b 100644
--- a/src/alerts/mattermost.rs
+++ b/src/alerts/mattermost.rs
@@ -54,11 +54,18 @@ pub fn build_payload(
         json!({ "short": true, "title": "Unknown",  "value": summary.unknown.to_string() }),
     ];
     if let Some(t) = &summary.target {
-        fields.push(json!({ "short": false, "title": "Target", "value": format!("`{t}`") }));
+        fields.push(json!({
+            "short": false,
+            "title": "Target",
+            "value": format!("`{}`", escape_for_code_span(t)),
+        }));
     }
     if !summary.by_rule.is_empty() {
-        let lines: Vec<String> =
-            summary.by_rule.iter().map(|(rule, count)| format!("• `{rule}` — {count}")).collect();
+        let lines: Vec<String> = summary
+            .by_rule
+            .iter()
+            .map(|(rule, count)| format!("• `{}` — {count}", escape_for_code_span(rule)))
+            .collect();
         fields.push(json!({
             "short": false,
             "title": "Top rules",
diff --git a/src/alerts/mod.rs b/src/alerts/mod.rs
index dccef16..e92420f 100644
--- a/src/alerts/mod.rs
+++ b/src/alerts/mod.rs
@@ -204,24 +204,66 @@ fn host_matches(host: &str, suffix: &str) -> bool {
     host == suffix || host.ends_with(&format!(".{suffix}"))
 }
 
-/// Validate a webhook URL: must parse, must use http(s) scheme, must have a
-/// host. Returns the parsed URL on success.
+/// Validate a webhook URL.
+///
+/// Webhook URLs typically embed a secret token in the path (e.g.
+/// `hooks.slack.com/services/T0/B0/<secret>`) and the payload contains
+/// finding metadata, so the transport must protect both. Default policy:
+///
+/// * Must parse and have a non-empty host.
+/// * Scheme must be `https`.
+/// * `http` is allowed *only* when the host is a loopback address
+///   (`localhost`, `127.0.0.0/8`, `::1`) — useful for local development and
+///   on-host webhook receivers without exposing webhooks-in-the-clear on a
+///   network.
 pub fn validate_webhook_url(url: &str) -> Result<()> {
     let parsed = url::Url::parse(url)
         .with_context(|| format!("invalid webhook URL `{}`", redact_for_log(url)))?;
     let scheme = parsed.scheme();
-    if scheme != "https" && scheme != "http" {
-        anyhow::bail!(
-            "webhook URL `{}` uses unsupported scheme `{scheme}` (only http/https are allowed)",
-            redact_for_log(url)
-        );
-    }
-    if parsed.host_str().is_none_or(|h| h.is_empty()) {
+    let host = parsed.host_str().unwrap_or("");
+    if host.is_empty() {
         anyhow::bail!("webhook URL `{}` has no host", redact_for_log(url));
     }
+    match scheme {
+        "https" => {}
+        "http" if is_loopback_host(host) => {}
+        "http" => {
+            anyhow::bail!(
+                "webhook URL `{}` uses cleartext `http://`; webhook tokens and finding \
+                 metadata must not traverse the network unencrypted. Use `https://`, or a \
+                 loopback host (`localhost`/`127.0.0.1`/`::1`) for local testing.",
+                redact_for_log(url)
+            );
+        }
+        _ => {
+            anyhow::bail!(
+                "webhook URL `{}` uses unsupported scheme `{scheme}` (only `https` is \
+                 allowed; `http` is allowed only for loopback hosts)",
+                redact_for_log(url)
+            );
+        }
+    }
     Ok(())
 }
 
+/// True when `host` resolves unambiguously to the local machine — i.e. the
+/// loopback hostname or any IPv4 in `127.0.0.0/8` or the IPv6 loopback `::1`.
+/// We deliberately do not consult DNS; only literal hostnames and IP
+/// literals count, so a malicious resolver cannot trick us into accepting
+/// `http://` for a remote host.
+fn is_loopback_host(host: &str) -> bool {
+    if host.eq_ignore_ascii_case("localhost") {
+        return true;
+    }
+    // `url::Url::host_str` keeps the surrounding `[...]` on IPv6 literals;
+    // `IpAddr::from_str` rejects that form, so strip the brackets first.
+    let trimmed = host.strip_prefix('[').and_then(|s| s.strip_suffix(']')).unwrap_or(host);
+    if let Ok(ip) = trimmed.parse::<std::net::IpAddr>() {
+        return ip.is_loopback();
+    }
+    false
+}
+
 fn redact_for_log(url: &str) -> String {
     redact_webhook(url)
 }
@@ -406,6 +448,42 @@ mod tests {
         assert_eq!(r, "<unparseable webhook url>");
     }
 
+    #[test]
+    fn validate_webhook_accepts_https() {
+        validate_webhook_url("https://hooks.slack.com/services/T0/B0/XXX").unwrap();
+    }
+
+    #[test]
+    fn validate_webhook_rejects_remote_http() {
+        let err = validate_webhook_url("http://example.com/hook").unwrap_err();
+        let msg = format!("{err:#}");
+        assert!(msg.contains("cleartext `http://`"), "got: {msg}");
+    }
+
+    #[test]
+    fn validate_webhook_allows_http_localhost() {
+        validate_webhook_url("http://localhost:8080/hook").unwrap();
+        validate_webhook_url("http://127.0.0.1:9000/hook").unwrap();
+        validate_webhook_url("http://[::1]:9000/hook").unwrap();
+    }
+
+    #[test]
+    fn validate_webhook_rejects_unknown_scheme() {
+        let err = validate_webhook_url("ftp://example.com/hook").unwrap_err();
+        let msg = format!("{err:#}");
+        assert!(msg.contains("unsupported scheme"), "got: {msg}");
+    }
+
+    #[test]
+    fn validate_webhook_rejects_no_host() {
+        // url::Url::parse on a relative-style file URL leaves no host.
+        let err = validate_webhook_url("file:///etc/passwd").unwrap_err();
+        let msg = format!("{err:#}");
+        // Either "no host" or "unsupported scheme" is acceptable; both are
+        // hard rejections.
+        assert!(msg.contains("no host") || msg.contains("unsupported scheme"), "got: {msg}");
+    }
+
     #[test]
     fn infer_format_slack() {
         assert_eq!(
diff --git a/src/alerts/slack.rs b/src/alerts/slack.rs
index 736b607..6cc2162 100644
--- a/src/alerts/slack.rs
+++ b/src/alerts/slack.rs
@@ -35,7 +35,7 @@ pub fn build_payload(
             "type": "section",
             "text": {
                 "type": "mrkdwn",
-                "text": format!("*Target:* `{}`", escape_mrkdwn(target))
+                "text": format!("*Target:* `{}`", escape_for_code_span(target))
             }
         }));
     }
@@ -44,7 +44,7 @@ pub fn build_payload(
         let lines: Vec<String> = summary
             .by_rule
             .iter()
-            .map(|(rule_id, count)| format!("• `{}` — {}", escape_mrkdwn(rule_id), count))
+            .map(|(rule_id, count)| format!("• `{}` — {}", escape_for_code_span(rule_id), count))
             .collect();
         blocks.push(json!({
             "type": "section",
@@ -66,12 +66,12 @@ pub fn build_payload(
             };
             detail_lines.push(format!(
                 "• `{}` at `{}:{}` — `{}` (validation: {}) — fp:`{}`",
-                escape_mrkdwn(&f.rule.id),
-                escape_mrkdwn(&f.finding.path),
+                escape_for_code_span(&f.rule.id),
+                escape_for_code_span(&f.finding.path),
                 f.finding.line,
                 snippet,
                 escape_mrkdwn(&f.finding.validation.status),
-                escape_mrkdwn(&f.finding.fingerprint),
+                escape_for_code_span(&f.finding.fingerprint),
             ));
         }
         if findings.len() > take {
@@ -98,12 +98,18 @@ pub fn build_payload(
     }
 
     if let Some(url) = &summary.report_url {
+        // Render as a Block Kit `actions` block with a `button` element. The
+        // button takes the URL via a separate JSON field, so we sidestep the
+        // mrkdwn `<url|text>` link syntax entirely — a URL containing `|` or
+        // `>` cannot inject markup or break the link the way it could in
+        // `<{}|Full report →>`.
         blocks.push(json!({
-            "type": "section",
-            "text": {
-                "type": "mrkdwn",
-                "text": format!("<{}|Full report →>", url)
-            }
+            "type": "actions",
+            "elements": [{
+                "type": "button",
+                "text": { "type": "plain_text", "text": "Full report" },
+                "url": url,
+            }]
         }));
     }