diff --git a/models/issues/issue_project.go b/models/issues/issue_project.go
index 5e0a337f7d6..c054fa3a434 100644
--- a/models/issues/issue_project.go
+++ b/models/issues/issue_project.go
@@ -124,6 +124,17 @@ func ChangeProjectAssign(issue *Issue, doer *user_model.User, newProjectID int64
 func addUpdateIssueProject(ctx context.Context, issue *Issue, doer *user_model.User, newProjectID int64) error {
 	oldProjectID := issue.projectID(ctx)
 
+	// Only check if we add a new project and not remove it.
+	if newProjectID > 0 {
+		newProject, err := project_model.GetProjectByID(ctx, newProjectID)
+		if err != nil {
+			return err
+		}
+		if newProject.RepoID != issue.RepoID {
+			return fmt.Errorf("issue's repository is not the same as project's repository")
+		}
+	}
+
 	if _, err := db.GetEngine(ctx).Where("project_issue.issue_id=?", issue.ID).Delete(&project_model.ProjectIssue{}); err != nil {
 		return err
 	}
diff --git a/models/issues/milestone.go b/models/issues/milestone.go
index 6c109591087..fba599e6ece 100644
--- a/models/issues/milestone.go
+++ b/models/issues/milestone.go
@@ -124,6 +124,11 @@ func NewMilestone(m *Milestone) (err error) {
 	return committer.Commit()
 }
 
+// HasMilestoneByRepoID returns if the milestone exists in the repository.
+func HasMilestoneByRepoID(ctx context.Context, repoID, id int64) (bool, error) {
+	return db.GetEngine(ctx).ID(id).Where("repo_id=?", repoID).Exist(new(Milestone))
+}
+
 // GetMilestoneByRepoID returns the milestone in a repository.
 func GetMilestoneByRepoID(ctx context.Context, repoID, id int64) (*Milestone, error) {
 	m := new(Milestone)
diff --git a/routers/api/v1/repo/pull_review.go b/routers/api/v1/repo/pull_review.go
index 57548f21029..1b61a40222d 100644
--- a/routers/api/v1/repo/pull_review.go
+++ b/routers/api/v1/repo/pull_review.go
@@ -886,7 +886,7 @@ func dismissReview(ctx *context.APIContext, msg string, isDismiss bool) {
 		return
 	}
 
-	_, err := pull_service.DismissReview(ctx, review.ID, msg, ctx.Doer, isDismiss)
+	_, err := pull_service.DismissReview(ctx, review.ID, ctx.Repo.Repository.ID, msg, ctx.Doer, isDismiss)
 	if err != nil {
 		ctx.Error(http.StatusInternalServerError, "pull_service.DismissReview", err)
 		return
diff --git a/routers/web/repo/issue.go b/routers/web/repo/issue.go
index 5b72ff79af3..e6f9529e31e 100644
--- a/routers/web/repo/issue.go
+++ b/routers/web/repo/issue.go
@@ -803,7 +803,8 @@ func NewIssue(ctx *context.Context) {
 	body := ctx.FormString("body")
 	ctx.Data["BodyQuery"] = body
 
-	ctx.Data["IsProjectsEnabled"] = ctx.Repo.CanRead(unit.TypeProjects)
+	isProjectsEnabled := ctx.Repo.CanRead(unit.TypeProjects)
+	ctx.Data["IsProjectsEnabled"] = isProjectsEnabled
 	ctx.Data["IsAttachmentEnabled"] = setting.Attachment.Enabled
 	upload.AddUploadContext(ctx, "comment")
 
@@ -819,7 +820,7 @@ func NewIssue(ctx *context.Context) {
 	}
 
 	projectID := ctx.FormInt64("project")
-	if projectID > 0 {
+	if projectID > 0 && isProjectsEnabled {
 		project, err := project_model.GetProjectByID(ctx, projectID)
 		if err != nil {
 			log.Error("GetProjectByID: %d: %v", projectID, err)
@@ -1043,6 +1044,11 @@ func NewIssuePost(ctx *context.Context) {
 	}
 
 	if projectID > 0 {
+		if !ctx.Repo.CanRead(unit.TypeProjects) {
+			// User must also be able to see the project.
+			ctx.Error(http.StatusBadRequest, "user hasn't permissions to read projects")
+			return
+		}
 		if err := issues_model.ChangeProjectAssign(issue, ctx.Doer, projectID); err != nil {
 			ctx.ServerError("ChangeProjectAssign", err)
 			return
@@ -1783,6 +1789,10 @@ func getActionIssues(ctx *context.Context) []*issues_model.Issue {
 	issueUnitEnabled := ctx.Repo.CanRead(unit.TypeIssues)
 	prUnitEnabled := ctx.Repo.CanRead(unit.TypePullRequests)
 	for _, issue := range issues {
+		if issue.RepoID != ctx.Repo.Repository.ID {
+			ctx.NotFound("some issue's RepoID is incorrect", errors.New("some issue's RepoID is incorrect"))
+			return nil
+		}
 		if issue.IsPull && !prUnitEnabled || !issue.IsPull && !issueUnitEnabled {
 			ctx.NotFound("IssueOrPullRequestUnitNotAllowed", nil)
 			return nil
diff --git a/routers/web/repo/projects.go b/routers/web/repo/projects.go
index 51c891dbf0b..71f264830d4 100644
--- a/routers/web/repo/projects.go
+++ b/routers/web/repo/projects.go
@@ -5,6 +5,7 @@
 package repo
 
 import (
+	"errors"
 	"fmt"
 	"net/http"
 	"net/url"
@@ -633,10 +634,17 @@ func MoveIssues(ctx *context.Context) {
 	}
 
 	if len(movedIssues) != len(form.Issues) {
-		ctx.ServerError("IssuesNotFound", err)
+		ctx.ServerError("some issues do not exist", errors.New("some issues do not exist"))
 		return
 	}
 
+	for _, issue := range movedIssues {
+		if issue.RepoID != project.RepoID {
+			ctx.ServerError("Some issue's repoID is not equal to project's repoID", errors.New("Some issue's repoID is not equal to project's repoID"))
+			return
+		}
+	}
+
 	if err = project_model.MoveIssuesOnProjectBoard(board, sortedIssueIDs); err != nil {
 		ctx.ServerError("MoveIssuesOnProjectBoard", err)
 		return
diff --git a/routers/web/repo/pull_review.go b/routers/web/repo/pull_review.go
index cc7ae9bbfa3..5a9f7a81389 100644
--- a/routers/web/repo/pull_review.go
+++ b/routers/web/repo/pull_review.go
@@ -5,6 +5,7 @@
 package repo
 
 import (
+	"errors"
 	"fmt"
 	"net/http"
 
@@ -118,6 +119,11 @@ func UpdateResolveConversation(ctx *context.Context) {
 		return
 	}
 
+	if comment.Issue.RepoID != ctx.Repo.Repository.ID {
+		ctx.NotFound("comment's repoID is incorrect", errors.New("comment's repoID is incorrect"))
+		return
+	}
+
 	var permResult bool
 	if permResult, err = issues_model.CanMarkConversation(comment.Issue, ctx.Doer); err != nil {
 		ctx.ServerError("CanMarkConversation", err)
@@ -236,7 +242,7 @@ func SubmitReview(ctx *context.Context) {
 // DismissReview dismissing stale review by repo admin
 func DismissReview(ctx *context.Context) {
 	form := web.GetForm(ctx).(*forms.DismissReviewForm)
-	comm, err := pull_service.DismissReview(ctx, form.ReviewID, form.Message, ctx.Doer, true)
+	comm, err := pull_service.DismissReview(ctx, form.ReviewID, ctx.Repo.Repository.ID, form.Message, ctx.Doer, true)
 	if err != nil {
 		ctx.ServerError("pull_service.DismissReview", err)
 		return
diff --git a/routers/web/web.go b/routers/web/web.go
index f8ea3877de8..d594caf6434 100644
--- a/routers/web/web.go
+++ b/routers/web/web.go
@@ -898,7 +898,7 @@ func RegisterRoutes(m *web.Route) {
 
 			m.Post("/labels", reqRepoIssuesOrPullsWriter, repo.UpdateIssueLabel)
 			m.Post("/milestone", reqRepoIssuesOrPullsWriter, repo.UpdateIssueMilestone)
-			m.Post("/projects", reqRepoIssuesOrPullsWriter, repo.UpdateIssueProject)
+			m.Post("/projects", reqRepoIssuesOrPullsWriter, reqRepoProjectsReader, repo.UpdateIssueProject)
 			m.Post("/assignee", reqRepoIssuesOrPullsWriter, repo.UpdateIssueAssignee)
 			m.Post("/request_review", reqRepoIssuesOrPullsReader, repo.UpdatePullReviewRequest)
 			m.Post("/dismiss_review", reqRepoAdmin, bindIgnErr(forms.DismissReviewForm{}), repo.DismissReview)
diff --git a/services/issue/milestone.go b/services/issue/milestone.go
index af337c3f142..d7c5fa45516 100644
--- a/services/issue/milestone.go
+++ b/services/issue/milestone.go
@@ -15,6 +15,17 @@ import (
 )
 
 func changeMilestoneAssign(ctx context.Context, doer *user_model.User, issue *issues_model.Issue, oldMilestoneID int64) error {
+	// Only check if milestone exists if we don't remove it.
+	if issue.MilestoneID > 0 {
+		has, err := issues_model.HasMilestoneByRepoID(ctx, issue.RepoID, issue.MilestoneID)
+		if err != nil {
+			return fmt.Errorf("HasMilestoneByRepoID: %v", err)
+		}
+		if !has {
+			return fmt.Errorf("HasMilestoneByRepoID: issue doesn't exist")
+		}
+	}
+
 	if err := issues_model.UpdateIssueCols(ctx, issue, "milestone_id"); err != nil {
 		return err
 	}
diff --git a/services/pull/review.go b/services/pull/review.go
index 9cb58fa3a15..b40e20a26f2 100644
--- a/services/pull/review.go
+++ b/services/pull/review.go
@@ -271,7 +271,7 @@ func SubmitReview(ctx context.Context, doer *user_model.User, gitRepo *git.Repos
 }
 
 // DismissReview dismissing stale review by repo admin
-func DismissReview(ctx context.Context, reviewID int64, message string, doer *user_model.User, isDismiss bool) (comment *issues_model.Comment, err error) {
+func DismissReview(ctx context.Context, reviewID, repoID int64, message string, doer *user_model.User, isDismiss bool) (comment *issues_model.Comment, err error) {
 	review, err := issues_model.GetReviewByID(ctx, reviewID)
 	if err != nil {
 		return
@@ -281,6 +281,16 @@ func DismissReview(ctx context.Context, reviewID int64, message string, doer *us
 		return nil, fmt.Errorf("not need to dismiss this review because it's type is not Approve or change request")
 	}
 
+	// load data for notify
+	if err = review.LoadAttributes(ctx); err != nil {
+		return nil, err
+	}
+
+	// Check if the review's repoID is the one we're currently expecting.
+	if review.Issue.RepoID != repoID {
+		return nil, fmt.Errorf("reviews's repository is not the same as the one we expect")
+	}
+
 	if err = issues_model.DismissReview(review, isDismiss); err != nil {
 		return
 	}
@@ -289,10 +299,6 @@ func DismissReview(ctx context.Context, reviewID int64, message string, doer *us
 		return nil, nil
 	}
 
-	// load data for notify
-	if err = review.LoadAttributes(ctx); err != nil {
-		return
-	}
 	if err = review.Issue.LoadPullRequest(); err != nil {
 		return
 	}