diff --git a/browser/app/winlauncher/freestanding/LoaderPrivateAPI.cpp b/browser/app/winlauncher/freestanding/LoaderPrivateAPI.cpp
index cc3d96f9ceba..40bc8ac63999 100644
--- a/browser/app/winlauncher/freestanding/LoaderPrivateAPI.cpp
+++ b/browser/app/winlauncher/freestanding/LoaderPrivateAPI.cpp
@@ -9,6 +9,7 @@
 #include "mozilla/Assertions.h"
 #include "mozilla/Types.h"
 #include "mozilla/Unused.h"
+#include "../DllBlocklistInit.h"
 
 using GlobalInitializerFn = void(__cdecl*)(void);
 
@@ -84,7 +85,7 @@ class MOZ_ONLY_USED_TO_AVOID_STATIC_CONSTRUCTORS LoaderPrivateAPIImp final
   void NotifyEndDllLoad(void* aContext, NTSTATUS aLoadNtStatus,
                         ModuleLoadInfo&& aModuleLoadInfo) final;
   nt::AllocatedUnicodeString GetSectionName(void* aSectionAddr) final;
-  nt::MemorySectionNameBuf GetSectionNameBuffer(void* aSectionAddr) final;
+  nt::LoaderAPI::InitDllBlocklistOOPFnPtr GetDllBlocklistInitFn() final;
 
   // LoaderPrivateAPI
   void NotifyBeginDllLoad(void** aContext,
@@ -93,6 +94,7 @@ class MOZ_ONLY_USED_TO_AVOID_STATIC_CONSTRUCTORS LoaderPrivateAPIImp final
                           PCUNICODE_STRING aRequestedDllName) final;
   void SetObserver(nt::LoaderObserver* aNewObserver) final;
   bool IsDefaultObserver() const final;
+  nt::MemorySectionNameBuf GetSectionNameBuffer(void* aSectionAddr) final;
 };
 
 static void Init() {
@@ -208,6 +210,11 @@ nt::AllocatedUnicodeString LoaderPrivateAPIImp::GetSectionName(
   return nt::AllocatedUnicodeString(&buf.mSectionFileName);
 }
 
+nt::LoaderAPI::InitDllBlocklistOOPFnPtr
+LoaderPrivateAPIImp::GetDllBlocklistInitFn() {
+  return &InitializeDllBlocklistOOP;
+}
+
 nt::MemorySectionNameBuf LoaderPrivateAPIImp::GetSectionNameBuffer(
     void* aSectionAddr) {
   const HANDLE kCurrentProcess = reinterpret_cast<HANDLE>(-1);
diff --git a/mozglue/dllservices/LoaderAPIInterfaces.h b/mozglue/dllservices/LoaderAPIInterfaces.h
index 63b56465a3b4..bff2642e83ea 100644
--- a/mozglue/dllservices/LoaderAPIInterfaces.h
+++ b/mozglue/dllservices/LoaderAPIInterfaces.h
@@ -92,6 +92,15 @@ class NS_NO_VTABLE LoaderAPI {
    * backing it.
    */
   virtual AllocatedUnicodeString GetSectionName(void* aSectionAddr) = 0;
+
+  using InitDllBlocklistOOPFnPtr =
+      LauncherVoidResultWithLineInfo (*)(const wchar_t*, HANDLE);
+
+  /**
+   * Return a pointer to the cross-process DLL Blocklist Init function.
+   * Used by sandboxBroker::LaunchApp.
+   */
+  virtual InitDllBlocklistOOPFnPtr GetDllBlocklistInitFn() = 0;
 };
 
 }  // namespace nt
diff --git a/mozglue/dllservices/ModuleLoadFrame.cpp b/mozglue/dllservices/ModuleLoadFrame.cpp
index f0a9225f930b..cb67f726bce4 100644
--- a/mozglue/dllservices/ModuleLoadFrame.cpp
+++ b/mozglue/dllservices/ModuleLoadFrame.cpp
@@ -28,7 +28,8 @@ nt::LoaderAPI* ModuleLoadFrame::sLoaderAPI;
 using GetNtLoaderAPIFn = decltype(&mozilla::GetNtLoaderAPI);
 
 /* static */
-void ModuleLoadFrame::StaticInit(nt::LoaderObserver* aNewObserver) {
+nt::LoaderAPI::InitDllBlocklistOOPFnPtr ModuleLoadFrame::StaticInit(
+    nt::LoaderObserver* aNewObserver) {
   const auto pGetNtLoaderAPI = reinterpret_cast<GetNtLoaderAPIFn>(
       ::GetProcAddress(::GetModuleHandleW(nullptr), "GetNtLoaderAPI"));
   if (!pGetNtLoaderAPI) {
@@ -36,10 +37,12 @@ void ModuleLoadFrame::StaticInit(nt::LoaderObserver* aNewObserver) {
     // the launcher process blocklist.
     gFallbackLoaderAPI.SetObserver(aNewObserver);
     sLoaderAPI = &gFallbackLoaderAPI;
-    return;
+    return nullptr;
   }
 
   sLoaderAPI = pGetNtLoaderAPI(aNewObserver);
+  MOZ_ASSERT(sLoaderAPI);
+  return sLoaderAPI->GetDllBlocklistInitFn();
 }
 
 ModuleLoadFrame::ModuleLoadFrame(PCUNICODE_STRING aRequestedDllName)
diff --git a/mozglue/dllservices/ModuleLoadFrame.h b/mozglue/dllservices/ModuleLoadFrame.h
index de8ef04f09ce..9a31455b8a56 100644
--- a/mozglue/dllservices/ModuleLoadFrame.h
+++ b/mozglue/dllservices/ModuleLoadFrame.h
@@ -25,7 +25,8 @@ class MOZ_RAII ModuleLoadFrame final {
   ModuleLoadFrame& operator=(const ModuleLoadFrame&) = delete;
   ModuleLoadFrame& operator=(ModuleLoadFrame&&) = delete;
 
-  static void StaticInit(nt::LoaderObserver* aNewObserver);
+  static nt::LoaderAPI::InitDllBlocklistOOPFnPtr StaticInit(
+      nt::LoaderObserver* aNewObserver);
 
  private:
   bool mAlreadyLoaded;
diff --git a/mozglue/dllservices/WindowsDllBlocklist.cpp b/mozglue/dllservices/WindowsDllBlocklist.cpp
index 6e30c724c91f..566455ebe530 100644
--- a/mozglue/dllservices/WindowsDllBlocklist.cpp
+++ b/mozglue/dllservices/WindowsDllBlocklist.cpp
@@ -588,6 +588,7 @@ static WindowsDllInterceptor Kernel32Intercept;
 static void GetNativeNtBlockSetWriter();
 
 static glue::LoaderObserver gMozglueLoaderObserver;
+static nt::LoaderAPI::InitDllBlocklistOOPFnPtr gInitDllBlocklistOOPFnPtr;
 
 MFBT_API void DllBlocklist_Initialize(uint32_t aInitFlags) {
   if (sBlocklistInitAttempted) {
@@ -597,7 +598,8 @@ MFBT_API void DllBlocklist_Initialize(uint32_t aInitFlags) {
 
   sInitFlags = aInitFlags;
 
-  glue::ModuleLoadFrame::StaticInit(&gMozglueLoaderObserver);
+  gInitDllBlocklistOOPFnPtr =
+      glue::ModuleLoadFrame::StaticInit(&gMozglueLoaderObserver);
 
 #ifdef _M_AMD64
   if (!IsWin8OrLater()) {
@@ -753,6 +755,7 @@ MFBT_API void DllBlocklist_SetFullDllServices(
   glue::AutoExclusiveLock lock(gDllServicesLock);
   if (aSvc) {
     aSvc->SetAuthenticodeImpl(GetAuthenticode());
+    aSvc->SetInitDllBlocklistOOPFnPtr(gInitDllBlocklistOOPFnPtr);
     gMozglueLoaderObserver.Forward(aSvc);
   }
 
diff --git a/mozglue/dllservices/WindowsDllServices.h b/mozglue/dllservices/WindowsDllServices.h
index 69cd12dd1049..cca67593ef47 100644
--- a/mozglue/dllservices/WindowsDllServices.h
+++ b/mozglue/dllservices/WindowsDllServices.h
@@ -10,10 +10,12 @@
 #include "mozilla/Assertions.h"
 #include "mozilla/Authenticode.h"
 #include "mozilla/LoaderAPIInterfaces.h"
+#include "mozilla/Move.h"
 #include "mozilla/mozalloc.h"
 #include "mozilla/UniquePtr.h"
 #include "mozilla/Vector.h"
 #include "mozilla/WindowsDllBlocklist.h"
+#include "mozilla/WinHeaderOnlyUtils.h"
 
 #if defined(MOZILLA_INTERNAL_API)
 
@@ -57,6 +59,17 @@ class DllServicesBase : public Authenticode {
     mAuthenticode = aAuthenticode;
   }
 
+  void SetInitDllBlocklistOOPFnPtr(
+      nt::LoaderAPI::InitDllBlocklistOOPFnPtr aPtr) {
+    mInitDllBlocklistOOPFnPtr = aPtr;
+  }
+
+  template <typename... Args>
+  LauncherVoidResultWithLineInfo InitDllBlocklistOOP(Args&&... aArgs) {
+    MOZ_RELEASE_ASSERT(mInitDllBlocklistOOPFnPtr);
+    return mInitDllBlocklistOOPFnPtr(std::forward<Args>(aArgs)...);
+  }
+
   // In debug builds we override GetBinaryOrgName to add a Gecko-specific
   // assertion. OTOH, we normally do not want people overriding this function,
   // so we'll make it final in the release case, thus covering all bases.
@@ -85,7 +98,8 @@ class DllServicesBase : public Authenticode {
   DllServicesBase& operator=(DllServicesBase&&) = delete;
 
  protected:
-  DllServicesBase() : mAuthenticode(nullptr) {}
+  DllServicesBase()
+      : mAuthenticode(nullptr), mInitDllBlocklistOOPFnPtr(nullptr) {}
 
   virtual ~DllServicesBase() = default;
 
@@ -94,6 +108,7 @@ class DllServicesBase : public Authenticode {
 
  private:
   Authenticode* mAuthenticode;
+  nt::LoaderAPI::InitDllBlocklistOOPFnPtr mInitDllBlocklistOOPFnPtr;
 };
 
 }  // namespace detail
diff --git a/mozglue/dllservices/WindowsFallbackLoaderAPI.cpp b/mozglue/dllservices/WindowsFallbackLoaderAPI.cpp
index 09cccee0615e..b57925c926de 100644
--- a/mozglue/dllservices/WindowsFallbackLoaderAPI.cpp
+++ b/mozglue/dllservices/WindowsFallbackLoaderAPI.cpp
@@ -67,6 +67,12 @@ nt::AllocatedUnicodeString FallbackLoaderAPI::GetSectionName(
   return nt::AllocatedUnicodeString(&buf.mSectionFileName);
 }
 
+nt::LoaderAPI::InitDllBlocklistOOPFnPtr
+FallbackLoaderAPI::GetDllBlocklistInitFn() {
+  MOZ_ASSERT_UNREACHABLE("This should not be called so soon!");
+  return nullptr;
+}
+
 void FallbackLoaderAPI::SetObserver(nt::LoaderObserver* aLoaderObserver) {
   mLoaderObserver = aLoaderObserver;
 }
diff --git a/mozglue/dllservices/WindowsFallbackLoaderAPI.h b/mozglue/dllservices/WindowsFallbackLoaderAPI.h
index 3232df71f376..cca5fadf1eb3 100644
--- a/mozglue/dllservices/WindowsFallbackLoaderAPI.h
+++ b/mozglue/dllservices/WindowsFallbackLoaderAPI.h
@@ -24,6 +24,7 @@ class MOZ_ONLY_USED_TO_AVOID_STATIC_CONSTRUCTORS FallbackLoaderAPI final
   void NotifyEndDllLoad(void* aContext, NTSTATUS aLoadNtStatus,
                         ModuleLoadInfo&& aModuleLoadInfo) final;
   nt::AllocatedUnicodeString GetSectionName(void* aSectionAddr) final;
+  nt::LoaderAPI::InitDllBlocklistOOPFnPtr GetDllBlocklistInitFn() final;
 
   void SetObserver(nt::LoaderObserver* aLoaderObserver);