diff --git a/Source/Core/WinUpdater/Platform.cpp b/Source/Core/WinUpdater/Platform.cpp
@@ -4,6 +4,7 @@
 #include <map>
 #include <optional>
 
+#include "Common/CommonPaths.h"
 #include "Common/FileUtil.h"
 #include "Common/HttpRequest.h"
 #include "Common/IOFile.h"
@@ -12,17 +13,106 @@
 
 #include "UpdaterCommon/Platform.h"
 #include "UpdaterCommon/UI.h"
+#include "UpdaterCommon/UpdaterCommon.h"
 
 namespace Platform
 {
-BuildInfo::BuildInfo(const std::string& content)
+struct BuildVersion
 {
-  map = {{"OSMinimumVersionWin10", ""},
-         {"OSMinimumVersionWin11", ""},
-         {"VCToolsVersion", ""},
-         {"VCToolsUpdateURL", ""}};
-  Parse(content);
-}
+  u32 major{};
+  u32 minor{};
+  u32 build{};
+  auto operator<=>(BuildVersion const& rhs) const = default;
+  static std::optional<BuildVersion> from_string(const std::string& str)
+  {
+    auto components = SplitString(str, '.');
+    // Allow variable number of components (truncating after "build"), but not
+    // empty.
+    if (components.size() == 0)
+      return {};
+    BuildVersion version;
+    if (!TryParse(components[0], &version.major, 10))
+      return {};
+    if (components.size() > 1 && !TryParse(components[1], &version.minor, 10))
+      return {};
+    if (components.size() > 2 && !TryParse(components[2], &version.build, 10))
+      return {};
+    return version;
+  }
+};
+
+enum class VersionCheckStatus
+{
+  NothingToDo,
+  UpdateOptional,
+  UpdateRequired,
+};
+
+struct VersionCheckResult
+{
+  VersionCheckStatus status{VersionCheckStatus::NothingToDo};
+  std::optional<BuildVersion> current_version{};
+  std::optional<BuildVersion> target_version{};
+};
+
+class BuildInfo
+{
+  using Map = std::map<std::string, std::string>;
+
+public:
+  BuildInfo() = default;
+  BuildInfo(const std::string& content)
+  {
+    map = {{"OSMinimumVersionWin10", ""},
+           {"OSMinimumVersionWin11", ""},
+           {"VCToolsVersion", ""},
+           {"VCToolsUpdateURL", ""}};
+    Parse(content);
+  }
+
+  std::optional<std::string> GetString(const std::string& name) const
+  {
+    auto it = map.find(name);
+    if (it == map.end() || it->second.size() == 0)
+      return {};
+    return it->second;
+  }
+
+  std::optional<BuildVersion> GetVersion(const std::string& name) const
+  {
+    auto str = GetString(name);
+    if (!str.has_value())
+      return {};
+    return BuildVersion::from_string(str.value());
+  }
+
+private:
+  void Parse(const std::string& content)
+  {
+    std::stringstream content_stream(content);
+    std::string line;
+    while (std::getline(content_stream, line))
+    {
+      if (line.starts_with("//"))
+        continue;
+      const size_t equals_index = line.find('=');
+      if (equals_index == line.npos)
+        continue;
+      auto key = line.substr(0, equals_index);
+      auto key_it = map.find(key);
+      if (key_it == map.end())
+        continue;
+      key_it->second = line.substr(equals_index + 1);
+    }
+  }
+  Map map;
+};
+
+struct BuildInfos
+{
+  BuildInfo current;
+  BuildInfo next;
+};
 
 // This default value should be kept in sync with the value of VCToolsUpdateURL in
 // build_info.txt.in
@@ -63,14 +153,13 @@ static std::optional<BuildVersion> GetInstalledVCRuntimeVersion()
   return version;
 }
 
-static VersionCheckResult VCRuntimeVersionCheck(const BuildInfo& this_build_info,
-                                                const BuildInfo& next_build_info)
+static VersionCheckResult VCRuntimeVersionCheck(const BuildInfos& build_infos)
 {
   VersionCheckResult result;
   result.current_version = GetInstalledVCRuntimeVersion();
-  result.target_version = next_build_info.GetVersion("VCToolsVersion");
+  result.target_version = build_infos.next.GetVersion("VCToolsVersion");
 
-  auto existing_version = this_build_info.GetVersion("VCToolsVersion");
+  auto existing_version = build_infos.current.GetVersion("VCToolsVersion");
 
   if (!result.target_version.has_value())
     result.status = VersionCheckStatus::UpdateOptional;
@@ -155,10 +244,45 @@ static VersionCheckResult OSVersionCheck(const BuildInfo& build_info)
   return result;
 }
 
-bool VersionCheck(const BuildInfo& this_build_info, const BuildInfo& next_build_info)
+std::optional<BuildInfos> InitBuildInfos(const std::vector<TodoList::UpdateOp>& to_update,
+                                         const std::string& install_base_path,
+                                         const std::string& temp_dir, FILE* log_fp)
 {
+  const auto op_it = std::find_if(to_update.cbegin(), to_update.cend(),
+                                  [&](const auto& op) { return op.filename == "build_info.txt"; });
+  if (op_it == to_update.cend())
+    return {};
+
+  const auto op = *op_it;
+  std::string build_info_path =
+      temp_dir + DIR_SEP + HexEncode(op.new_hash.data(), op.new_hash.size());
+  std::string build_info_content;
+  if (!File::ReadFileToString(build_info_path, build_info_content) ||
+      op.new_hash != ComputeHash(build_info_content))
+  {
+    fprintf(log_fp, "Failed to read %s\n.", build_info_path.c_str());
+    return {};
+  }
+  BuildInfos build_infos;
+  build_infos.next = Platform::BuildInfo(build_info_content);
+
+  build_info_path = install_base_path + DIR_SEP + "build_info.txt";
+  build_infos.current = Platform::BuildInfo();
+  if (File::ReadFileToString(build_info_path, build_info_content))
+  {
+    if (op.old_hash != ComputeHash(build_info_content))
+      fprintf(log_fp, "Using modified existing BuildInfo %s.\n", build_info_path.c_str());
+    build_infos.current = Platform::BuildInfo(build_info_content);
+  }
+  return build_infos;
+}
+
+bool CheckBuildInfo(const BuildInfos& build_infos)
+{
+  // The existing BuildInfo may have been modified. Be careful not to overly trust its contents!
+
   // If the binary requires more recent OS, inform the user.
-  auto os_check = OSVersionCheck(next_build_info);
+  auto os_check = OSVersionCheck(build_infos.next);
   if (os_check.status == VersionCheckStatus::UpdateRequired)
   {
     UI::Error("Please update Windows in order to update Dolphin.");
@@ -167,13 +291,13 @@ bool VersionCheck(const BuildInfo& this_build_info, const BuildInfo& next_build_
 
   // Check if application being launched needs more recent version of VC Redist. If so, download
   // latest updater and execute it.
-  auto vc_check = VCRuntimeVersionCheck(this_build_info, next_build_info);
+  auto vc_check = VCRuntimeVersionCheck(build_infos);
   if (vc_check.status != VersionCheckStatus::NothingToDo)
   {
     // Don't bother checking status of the install itself, just check if we actually see the new
     // version.
-    VCRuntimeUpdate(next_build_info);
-    vc_check = VCRuntimeVersionCheck(this_build_info, next_build_info);
+    VCRuntimeUpdate(build_infos.next);
+    vc_check = VCRuntimeVersionCheck(build_infos);
     if (vc_check.status == VersionCheckStatus::UpdateRequired)
     {
       // The update is required and the install failed for some reason.
@@ -184,4 +308,17 @@ bool VersionCheck(const BuildInfo& this_build_info, const BuildInfo& next_build_
 
   return true;
 }
+
+bool VersionCheck(const std::vector<TodoList::UpdateOp>& to_update,
+                  const std::string& install_base_path, const std::string& temp_dir, FILE* log_fp)
+{
+  auto build_infos = InitBuildInfos(to_update, install_base_path, temp_dir, log_fp);
+  // If there's no build info, it means the check should be skipped.
+  if (!build_infos.has_value())
+  {
+    return true;
+  }
+  return CheckBuildInfo(build_infos.value());
+}
+
 }  // namespace Platform