diff --git a/api/Element.json b/api/Element.json
index e22ca5f4ffa4a8..056d5935f46cbc 100644
--- a/api/Element.json
+++ b/api/Element.json
@@ -10328,7 +10328,15 @@
             "chrome_android": "mirror",
             "edge": "mirror",
             "firefox": {
-              "version_added": "148"
+              "version_added": "138",
+              "flags": [
+                {
+                  "type": "preference",
+                  "name": "dom.security.sanitizer.enabled",
+                  "value_to_set": "true"
+                }
+              ],
+              "notes": "Available by default in Nightly."
             },
             "firefox_android": "mirror",
             "oculus": "mirror",
diff --git a/api/Sanitizer.json b/api/Sanitizer.json
index 2aeade70519472..232bded49b800b 100644
--- a/api/Sanitizer.json
+++ b/api/Sanitizer.json
@@ -14,7 +14,15 @@
           "chrome_android": "mirror",
           "edge": "mirror",
           "firefox": {
-            "version_added": "148"
+            "version_added": "138",
+            "flags": [
+              {
+                "type": "preference",
+                "name": "dom.security.sanitizer.enabled",
+                "value_to_set": "true"
+              }
+            ],
+            "notes": "Available by default in Nightly."
           },
           "firefox_android": "mirror",
           "oculus": "mirror",
@@ -48,7 +56,15 @@
             "chrome_android": "mirror",
             "edge": "mirror",
             "firefox": {
-              "version_added": "148"
+              "version_added": "138",
+              "flags": [
+                {
+                  "type": "preference",
+                  "name": "dom.security.sanitizer.enabled",
+                  "value_to_set": "true"
+                }
+              ],
+              "notes": "Available by default in Nightly."
             },
             "firefox_android": "mirror",
             "oculus": "mirror",
@@ -83,7 +99,15 @@
             "chrome_android": "mirror",
             "edge": "mirror",
             "firefox": {
-              "version_added": "148"
+              "version_added": "138",
+              "flags": [
+                {
+                  "type": "preference",
+                  "name": "dom.security.sanitizer.enabled",
+                  "value_to_set": "true"
+                }
+              ],
+              "notes": "Available by default in Nightly."
             },
             "firefox_android": "mirror",
             "oculus": "mirror",
@@ -118,7 +142,15 @@
             "chrome_android": "mirror",
             "edge": "mirror",
             "firefox": {
-              "version_added": "148"
+              "version_added": "138",
+              "flags": [
+                {
+                  "type": "preference",
+                  "name": "dom.security.sanitizer.enabled",
+                  "value_to_set": "true"
+                }
+              ],
+              "notes": "Available by default in Nightly."
             },
             "firefox_android": "mirror",
             "oculus": "mirror",
@@ -153,7 +185,15 @@
             "chrome_android": "mirror",
             "edge": "mirror",
             "firefox": {
-              "version_added": "148"
+              "version_added": "138",
+              "flags": [
+                {
+                  "type": "preference",
+                  "name": "dom.security.sanitizer.enabled",
+                  "value_to_set": "true"
+                }
+              ],
+              "notes": "Available by default in Nightly."
             },
             "firefox_android": "mirror",
             "oculus": "mirror",
@@ -188,7 +228,15 @@
             "chrome_android": "mirror",
             "edge": "mirror",
             "firefox": {
-              "version_added": "148"
+              "version_added": "138",
+              "flags": [
+                {
+                  "type": "preference",
+                  "name": "dom.security.sanitizer.enabled",
+                  "value_to_set": "true"
+                }
+              ],
+              "notes": "Available by default in Nightly."
             },
             "firefox_android": "mirror",
             "oculus": "mirror",
@@ -223,7 +271,15 @@
             "chrome_android": "mirror",
             "edge": "mirror",
             "firefox": {
-              "version_added": "148"
+              "version_added": "138",
+              "flags": [
+                {
+                  "type": "preference",
+                  "name": "dom.security.sanitizer.enabled",
+                  "value_to_set": "true"
+                }
+              ],
+              "notes": "Available by default in Nightly."
             },
             "firefox_android": "mirror",
             "oculus": "mirror",
@@ -258,7 +314,15 @@
             "chrome_android": "mirror",
             "edge": "mirror",
             "firefox": {
-              "version_added": "148"
+              "version_added": "138",
+              "flags": [
+                {
+                  "type": "preference",
+                  "name": "dom.security.sanitizer.enabled",
+                  "value_to_set": "true"
+                }
+              ],
+              "notes": "Available by default in Nightly."
             },
             "firefox_android": "mirror",
             "oculus": "mirror",
@@ -293,7 +357,15 @@
             "chrome_android": "mirror",
             "edge": "mirror",
             "firefox": {
-              "version_added": "148"
+              "version_added": "138",
+              "flags": [
+                {
+                  "type": "preference",
+                  "name": "dom.security.sanitizer.enabled",
+                  "value_to_set": "true"
+                }
+              ],
+              "notes": "Available by default in Nightly."
             },
             "firefox_android": "mirror",
             "oculus": "mirror",
@@ -328,7 +400,15 @@
             "chrome_android": "mirror",
             "edge": "mirror",
             "firefox": {
-              "version_added": "148"
+              "version_added": "138",
+              "flags": [
+                {
+                  "type": "preference",
+                  "name": "dom.security.sanitizer.enabled",
+                  "value_to_set": "true"
+                }
+              ],
+              "notes": "Available by default in Nightly."
             },
             "firefox_android": "mirror",
             "oculus": "mirror",
@@ -363,7 +443,15 @@
             "chrome_android": "mirror",
             "edge": "mirror",
             "firefox": {
-              "version_added": "148"
+              "version_added": "138",
+              "flags": [
+                {
+                  "type": "preference",
+                  "name": "dom.security.sanitizer.enabled",
+                  "value_to_set": "true"
+                }
+              ],
+              "notes": "Available by default in Nightly."
             },
             "firefox_android": "mirror",
             "oculus": "mirror",