diff --git a/.changeset/mask-encoded-secrets.md b/.changeset/mask-encoded-secrets.md
new file mode 100644
index 0000000000..5e5c51ecc7
--- /dev/null
+++ b/.changeset/mask-encoded-secrets.md
@@ -0,0 +1,5 @@
+---
+'@redocly/respect-core': patch
+---
+
+Fixed an issue where secrets masking did not cover encoded secrets in `har-output`.
diff --git a/packages/respect-core/src/modules/__tests__/logger-output/mask-secrets.test.ts b/packages/respect-core/src/modules/__tests__/logger-output/mask-secrets.test.ts
index 76f8b8b3d7..71f3194269 100644
--- a/packages/respect-core/src/modules/__tests__/logger-output/mask-secrets.test.ts
+++ b/packages/respect-core/src/modules/__tests__/logger-output/mask-secrets.test.ts
@@ -103,6 +103,67 @@ describe('maskSecrets', () => {
     expect(result).toEqual('Bearer ********');
   });
 
+  it('should mask a URL-encoded occurrence of a secret', () => {
+    const result = maskSecrets('password=p%40ss+word', new Set(['p@ss word']));
+    expect(result).toEqual('password=********');
+  });
+
+  it('should mask a JSON-escaped occurrence of a secret', () => {
+    const result = maskSecrets(JSON.stringify({ password: 'pa"ss' }), new Set(['pa"ss']));
+    expect(result).toEqual('{"password":"********"}');
+  });
+
+  it('should mask every occurrence of a secret within one value', () => {
+    const result = maskSecrets(
+      { body: '{"password":"hunter2","confirmPassword":"hunter2"}' },
+      new Set(['hunter2'])
+    );
+    expect(result).toEqual({ body: '{"password":"********","confirmPassword":"********"}' });
+  });
+
+  it('should mask secrets everywhere in a HAR capture', () => {
+    const har = {
+      log: {
+        entries: [
+          {
+            request: {
+              headers: [{ name: 'authorization', value: 'Bearer hunter2' }],
+              postData: {
+                mimeType: 'application/x-www-form-urlencoded',
+                text: 'password=p%40ss+word',
+              },
+            },
+            response: {
+              content: { mimeType: 'application/json', text: '{"token":"hunter2"}' },
+            },
+          },
+        ],
+      },
+    };
+
+    const result = maskSecrets(har, new Set(['hunter2', 'p@ss word']));
+
+    expect(result.log.entries[0].request.headers[0].value).toBe('Bearer ********');
+    expect(result.log.entries[0].request.postData.text).toBe('password=********');
+    expect(result.log.entries[0].response.content.text).toBe('{"token":"********"}');
+  });
+
+  it('should mask a longer secret that starts with a shorter one', () => {
+    const result = maskSecrets('Bearer passphrase123', new Set(['pass', 'passphrase123']));
+    expect(result).toEqual('Bearer ********');
+  });
+
+  it('should ignore a whitespace-only secret', () => {
+    const result = maskSecrets('filter=a+b', new Set([' ']));
+    expect(result).toEqual('filter=a+b');
+  });
+
+  it('should mask a secret containing a lone surrogate', () => {
+    const secret = `tok${String.fromCharCode(0xd800)}en`;
+    const result = maskSecrets({ access_token: secret }, new Set([secret]));
+    expect(result).toEqual({ access_token: '********' });
+  });
+
   it('should preserve ArrayBuffer objects without breaking them', () => {
     const originalArrayBuffer = new ArrayBuffer(8);
     const originalData = new Uint8Array(originalArrayBuffer);
diff --git a/packages/respect-core/src/modules/logger-output/mask-secrets.ts b/packages/respect-core/src/modules/logger-output/mask-secrets.ts
index fa17917746..3bc5a7fc0e 100644
--- a/packages/respect-core/src/modules/logger-output/mask-secrets.ts
+++ b/packages/respect-core/src/modules/logger-output/mask-secrets.ts
@@ -10,39 +10,56 @@ export const POTENTIALLY_SECRET_FIELDS = [
   'client_secret',
 ];
 
+/**
+ * A secret can appear in a log or capture already encoded: a JSON body
+ * escapes quotes and backslashes, a form-urlencoded body or a URL
+ * percent-encodes special characters. Mask those variants along with the
+ * raw value.
+ */
+function collectSecretPatterns(secretsSet: Set<string>): string[] {
+  const patterns = new Set<string>();
+  for (const secret of secretsSet) {
+    if (!secret.trim()) continue;
+    patterns.add(secret);
+    patterns.add(JSON.stringify(secret).slice(1, -1));
+    // A lone surrogate reaching us through a captured `\uD800` escape makes
+    // encodeURIComponent throw; URLSearchParams substitutes U+FFFD instead.
+    if (secret.isWellFormed()) {
+      patterns.add(encodeURIComponent(secret));
+    }
+    // URLSearchParams serializes to `secret=value`; drop the key to keep
+    // the form-urlencoded variant (spaces become `+`, unlike encodeURIComponent).
+    patterns.add(new URLSearchParams([['secret', secret]]).toString().slice('secret='.length));
+  }
+  // Longest first: a short secret nested in a longer one would otherwise mask
+  // only the prefix and leave the rest of the longer secret visible.
+  return Array.from(patterns).sort((left, right) => right.length - left.length);
+}
+
 export function maskSecrets<T extends { [x: string]: any } | string>(
   target: T,
   secretsSet: Set<string>
 ): T {
-  const maskValue = (value: string, secret: string): string => {
-    return value.replace(secret, '*'.repeat(8));
-  };
-
-  if (typeof target === 'string') {
-    let maskedString = target as string;
-    secretsSet.forEach((secret) => {
-      maskedString = maskedString.split(secret).join('*'.repeat(8));
-    });
-    return maskedString as T;
-  }
-
-  const masked = deepCopy(target);
-  const maskIfContainsSecret = (value: string): string => {
+  const patterns = collectSecretPatterns(secretsSet);
+  const maskString = (value: string): string => {
     let maskedValue = value;
-
-    for (const secret of secretsSet) {
-      if (maskedValue.includes(secret)) {
-        maskedValue = maskValue(maskedValue, secret);
+    for (const pattern of patterns) {
+      if (maskedValue.includes(pattern)) {
+        maskedValue = maskedValue.split(pattern).join('*'.repeat(8));
       }
     }
-
     return maskedValue;
   };
 
+  if (typeof target === 'string') {
+    return maskString(target) as T;
+  }
+
+  const masked = deepCopy(target);
   const maskRecursive = (current: any) => {
     for (const key in current) {
       if (typeof current[key] === 'string') {
-        current[key] = maskIfContainsSecret(current[key]);
+        current[key] = maskString(current[key]);
       } else if (isPlainObject(current[key]) || Array.isArray(current[key])) {
         // Skip special objects that should not be modified
         if (