diff --git a/.gitignore b/.gitignore
index 9620ab5..f812fa4 100644
--- a/.gitignore
+++ b/.gitignore
@@ -627,3 +627,4 @@ firefox-3.6.4.source.tar.bz2
 /firefox-langpacks-124.0-20240313.tar.xz
 /firefox-124.0.1.source.tar.xz
 /firefox-langpacks-124.0.1-20240322.tar.xz
+/wasi-sdk-20.tar.gz
diff --git a/firefox-mozconfig b/firefox-mozconfig
index 676a0e0..272b265 100644
--- a/firefox-mozconfig
+++ b/firefox-mozconfig
@@ -14,8 +14,6 @@ ac_add_options --allow-addon-sideload
 ac_add_options --with-system-fdk-aac
 ac_add_options --enable-js-shell
 ac_add_options --with-unsigned-addon-scopes=app,system
-ac_add_options --without-sysroot
-ac_add_options --without-wasm-sandboxed-libraries
 
 export BUILD_OFFICIAL=1
 export MOZILLA_OFFICIAL=1
diff --git a/firefox.spec b/firefox.spec
index 12e050f..d2e8b42 100644
--- a/firefox.spec
+++ b/firefox.spec
@@ -33,6 +33,12 @@ ExcludeArch: i686
 %else
 %global enable_replace_malloc 0
 %endif
++# wasi_sdk is for sandboxing third party c/c++ libs by using rlbox
++%ifarch s390x
++%bcond wasi_sdk 0
++%else
++%bcond wasi_sdk 1
++%endif
 
 %if "%{toolchain}" == "clang"
 %global build_with_clang 1
@@ -216,6 +222,8 @@ Source45:       run-wayland-compositor
 Source46:       org.mozilla.firefox.SearchProvider.service
 Source47:       org.mozilla.firefox.desktop
 Source48:       org.mozilla.firefox.appdata.xml.in
+Source49:       wasi.patch.template
+Source50:      wasi-sdk-20-1.fc39.src.rpm
 
 # Build patches
 #Patch3:         mozilla-build-arm.patch
@@ -234,6 +242,7 @@ Patch61:        firefox-glibc-dynstack.patch
 Patch71:        0001-GLIBCXX-fix-for-GCC-12.patch
 Patch78:        firefox-i686-build.patch
 Patch79:        firefox-gcc-13-build.patch
+Patch80:        wasi.patch
 
 # Test patches
 # Generate without context by
@@ -320,7 +329,7 @@ BuildRequires:  llvm
 BuildRequires:  llvm-devel
 BuildRequires:  clang
 BuildRequires:  clang-libs
-%if %{build_with_clang}
+%if %{build_with_clang} || %{with wasi_sdk}
 BuildRequires:  lld
 %endif
 
@@ -443,6 +452,9 @@ BuildRequires:  libproxy-devel
 %if %{enable_replace_malloc}
 BuildRequires:  libstdc++-static
 %endif
+%if %{with wasi_sdk}
+BuildRequires:  clang cmake ninja-build
+%endif
 
 Obsoletes:      mozilla <= 37:1.7.13
 Provides:       webclient
@@ -540,6 +552,13 @@ This package contains results of tests executed during build.
 %patch78 -p1 -b .firefox-i686
 %patch79 -p1 -b .firefox-gcc-13-build
 
+# We need to create the wasi.patch with the correct path to the wasm libclang_rt.
+%if %{with wasi_sdk}
+export LIBCLANG_RT=%{_topdir}/BUILDROOT/usr/share/wasi-sysroot/lib/libclang_rt.builtins-wasm32.a; cat %{SOURCE49} | envsubst > %{_sourcedir}/wasi.patch
+cat %{_sourcedir}/wasi.patch
+%patch80 -p1 -b .wasi
+%endif
+
 # Test patches
 #%patch100 -p1 -b .firefox-tests-xpcshell
 #%patch101 -p1 -b .firefox-tests-reftest
@@ -711,6 +730,43 @@ chmod a-x third_party/rust/ash/src/extensions/nv/*.rs
 # Is that already fixed?
 %define _lto_cflags %{nil}
 
+#WASI SDK
+%if %{with wasi_sdk}
+function install_rpms_to_current_dir() {
+    PACKAGE_RPM=$(eval echo $1)
+    #PACKAGE_DIR=%{_rpmdir}
+    PACKAGE_DIR=%{_topdir}/RPMS
+
+    if [ ! -f $PACKAGE_DIR/$PACKAGE_RPM ]; then
+        # Hack for tps tests
+        ARCH_STR=%{_arch}
+        %ifarch %{ix86}
+            ARCH_STR="i?86"
+        %endif
+        PACKAGE_DIR="$PACKAGE_DIR/$ARCH_STR"
+     fi
+
+     for package in $(ls $PACKAGE_DIR/$PACKAGE_RPM)
+     do
+         echo "$package"
+         rpm2cpio "$package" | cpio -idu
+         rm -f "$package"
+     done
+}
+
+rpm -ivh %{SOURCE50}
+#export CC="clang"
+#export CXX="clang++"
+#eport AR="clang-ar"
+#export NM="clang-nm"
+#export RANLIB="clang-ranlib"
+rpmbuild --nodeps -bb --noclean %{_topdir}/SPECS/wasi-sdk.spec
+pushd %{_buildrootdir}
+install_rpms_to_current_dir wasi-sdk-20*.rpm
+popd
+%endif 
+# ^ with wasi_sdk
+
 %if 0%{?use_bundled_cbindgen}
 mkdir -p my_rust_vendor
 cd my_rust_vendor
@@ -824,6 +880,13 @@ env | grep GCOV
 echo "ac_add_options --enable-lto" >> .mozconfig
 echo "ac_add_options MOZ_PGO=1" >> .mozconfig
 %endif
+ 
+%if %{with wasi_sdk}
+echo "ac_add_options --with-wasi-sysroot=%{_topdir}/BUILDROOT/usr/share/wasi-sysroot" >> .mozconfig
+%else
+echo "ac_add_options --without-sysroot" >> .mozconfig
+echo "ac_add_options --without-wasm-sandboxed-libraries" >> .mozconfig
+%endif
 
 # Require 4 GB of RAM per CPU core
 %constrain_build -m 4096
diff --git a/sources b/sources
index 5511afe..72d52ad 100644
--- a/sources
+++ b/sources
@@ -3,3 +3,4 @@ SHA512 (cbindgen-vendor.tar.xz) = 3e7eaff088db918e95f5505e5feeb06e8b7b95cc62042a
 SHA512 (dump_syms-vendor.tar.xz) = 5769c052fa874a965eb8837776b01fb097e8930f45d0d0d2a93997c4fae8726184a192aee52302bde62e62897801b1463cae9283563d9d60e8b8ee80a250f2a3
 SHA512 (firefox-124.0.1.source.tar.xz) = 282c45e5c468419536dd8b81c8ea687b10d8002d7521403330e6eeef49207143bee88a44c3785748d461ed9a72687606f5da14f4dfb98eb40a5cd08a4a12722b
 SHA512 (firefox-langpacks-124.0.1-20240322.tar.xz) = bc7f93493636cc4d9845df2583cdd6cc941e284e35afb2bfe2e0ad32c05dc554c4af22e3d9703ce03a48f30e6858e300dea1c892d2f896be1db58581c81339fd
+SHA512 (wasi-sdk-20.tar.gz) = 95be9d9b41ed1f7884e9cd68bad22abbb355b049fd09731c89b9e36666d0205b1a16ec9c21820adf0c5a34e2048015cbfbef0542170d466fa3336c636873c405
diff --git a/wasi.patch b/wasi.patch
new file mode 100644
index 0000000..b47b496
--- /dev/null
+++ b/wasi.patch
@@ -0,0 +1,12 @@
+diff -up firefox-121.0.1/toolkit/moz.configure.wasi firefox-121.0.1/toolkit/moz.configure
+--- firefox-121.0.1/toolkit/moz.configure.wasi	2024-02-01 09:14:33.816548952 +0100
++++ firefox-121.0.1/toolkit/moz.configure	2024-02-01 09:15:53.264684309 +0100
+@@ -2663,7 +2663,7 @@ with only_when(requires_wasm_sandboxing
+     def wasi_sysroot_flags(wasi_sysroot):
+         if wasi_sysroot:
+             log.info("Using wasi sysroot in %s", wasi_sysroot)
+-            return ["--sysroot=%s" % wasi_sysroot]
++            return ["--sysroot=%s" % wasi_sysroot, "-nodefaultlibs",  "-lc", "-lwasi-emulated-process-clocks", "-lc++", "-lc++abi", "/home/jhorak/rpmbuild/BUILDROOT/usr/share/wasi-sysroot/lib/libclang_rt.builtins-wasm32.a"]
+         return []
+ 
+     set_config("WASI_SYSROOT", wasi_sysroot)
diff --git a/wasi.patch.template b/wasi.patch.template
new file mode 100644
index 0000000..aa2838e
--- /dev/null
+++ b/wasi.patch.template
@@ -0,0 +1,12 @@
+diff -up firefox-121.0.1/toolkit/moz.configure.wasi firefox-121.0.1/toolkit/moz.configure
+--- firefox-121.0.1/toolkit/moz.configure.wasi	2024-02-01 09:14:33.816548952 +0100
++++ firefox-121.0.1/toolkit/moz.configure	2024-02-01 09:15:53.264684309 +0100
+@@ -2663,7 +2663,7 @@ with only_when(requires_wasm_sandboxing
+     def wasi_sysroot_flags(wasi_sysroot):
+         if wasi_sysroot:
+             log.info("Using wasi sysroot in %s", wasi_sysroot)
+-            return ["--sysroot=%s" % wasi_sysroot]
++            return ["--sysroot=%s" % wasi_sysroot, "-nodefaultlibs",  "-lc", "-lwasi-emulated-process-clocks", "-lc++", "-lc++abi", "$LIBCLANG_RT"]
+         return []
+ 
+     set_config("WASI_SYSROOT", wasi_sysroot)