diff --git a/apps/desktop/scripts/notarize-artifact.cjs b/apps/desktop/scripts/notarize-artifact.cjs
index ab8fef7387e..89a4901c5cc 100644
--- a/apps/desktop/scripts/notarize-artifact.cjs
+++ b/apps/desktop/scripts/notarize-artifact.cjs
@@ -7,7 +7,10 @@ function run(command, args) {
   return new Promise((resolve, reject) => {
     execFile(command, args, (error, stdout, stderr) => {
       if (error) {
-        reject(new Error(`${command} ${args.join(' ')} failed: ${stderr?.trim() || stdout?.trim() || error.message}`))
+        // Intentionally omit args from the rejection message: callers pass
+        // notarization credentials (key id, issuer, key file path) here, and
+        // surfacing them in error output would land in CI logs.
+        reject(new Error(`${command} failed: ${stderr?.trim() || stdout?.trim() || error.message}`))
         return
       }
       resolve()
diff --git a/apps/desktop/src/app/settings/helpers.ts b/apps/desktop/src/app/settings/helpers.ts
index 7c17a3b2c31..b1723009ccc 100644
--- a/apps/desktop/src/app/settings/helpers.ts
+++ b/apps/desktop/src/app/settings/helpers.ts
@@ -25,16 +25,32 @@ export const providerPriority = (name: string) => PROVIDER_GROUPS.find(g => g.na
 
 const POLLUTING_PATH_PARTS = new Set(['__proto__', 'constructor', 'prototype'])
 
+function isSafePart(part: string): boolean {
+  return part.length > 0 && !POLLUTING_PATH_PARTS.has(part)
+}
+
 function configPathParts(path: string): string[] {
   const parts = path.split('.')
 
-  if (parts.some(part => !part || POLLUTING_PATH_PARTS.has(part))) {
+  if (!parts.every(isSafePart)) {
     throw new Error(`Unsafe config path: ${path}`)
   }
 
   return parts
 }
 
+function safeSet(target: Record<string, unknown>, key: string, value: unknown): void {
+  if (!isSafePart(key)) {
+    throw new Error(`Unsafe config key: ${key}`)
+  }
+  Object.defineProperty(target, key, {
+    value,
+    writable: true,
+    enumerable: true,
+    configurable: true,
+  })
+}
+
 export function getNested(obj: HermesConfigRecord, path: string): unknown {
   let cur: unknown = obj
 
@@ -43,6 +59,10 @@ export function getNested(obj: HermesConfigRecord, path: string): unknown {
       return undefined
     }
 
+    if (!Object.prototype.hasOwnProperty.call(cur, part)) {
+      return undefined
+    }
+
     cur = (cur as Record<string, unknown>)[part]
   }
 
@@ -57,14 +77,20 @@ export function setNested(obj: HermesConfigRecord, path: string, value: unknown)
   for (let i = 0; i < parts.length - 1; i += 1) {
     const part = parts[i]
 
-    if (cur[part] == null || typeof cur[part] !== 'object') {
-      cur[part] = {}
+    if (!isSafePart(part)) {
+      throw new Error(`Unsafe config path part: ${part}`)
+    }
+
+    const existing = Object.prototype.hasOwnProperty.call(cur, part) ? cur[part] : undefined
+
+    if (existing == null || typeof existing !== 'object') {
+      safeSet(cur, part, {})
     }
 
     cur = cur[part] as Record<string, unknown>
   }
 
-  cur[parts[parts.length - 1]] = value
+  safeSet(cur, parts[parts.length - 1], value)
 
   return clone
 }
diff --git a/apps/desktop/src/lib/markdown-preprocess.ts b/apps/desktop/src/lib/markdown-preprocess.ts
index 17347bbfc68..e08aef06291 100644
--- a/apps/desktop/src/lib/markdown-preprocess.ts
+++ b/apps/desktop/src/lib/markdown-preprocess.ts
@@ -32,7 +32,12 @@ function scrubBacktickNoise(text: string): string {
     const marker = match[2] || '```'
     const info = match[3] || ''
     const body = match[4] || ''
-    const closeRe = new RegExp(`\\n[ \\t]*${marker.replace(/[.*+?^${}()|[\]\\]/g, '\\$&')}[ \\t]*(?=\\n|$)`)
+    // `marker` is captured by `(`{3,}|~{3,})` above, so its only meta-character
+    // is the backtick or tilde. Reconstruct the close-fence pattern from a
+    // literal char + length to keep the regex source free of tainted input
+    // (and to keep CodeQL's hostname-regexp dataflow happy).
+    const fenceChar = marker[0] === '~' ? '\\~' : '`'
+    const closeRe = new RegExp(`\\n[ \\t]*${fenceChar}{${marker.length}}[ \\t]*(?=\\n|$)`)
 
     if (!closeRe.test(body) && sanitizeLanguageTag(info) && !isLikelyProseFence(info, body)) {
       protectedRanges.push({ end: text.length, start })