Implement content filtering for issues, PRs, and comments

Co-authored-by: SamMorrowDrums <[email protected]>

Author: Copilot

README.md

@@ -219,6 +219,41 @@ docker run -i --rm \
   ghcr.io/github/github-mcp-server
 ```
 
+## Content Filtering
+
+The GitHub MCP Server includes a content filtering feature that removes invisible characters and hidden content from GitHub issues, PRs, and comments. This helps prevent potential security risks and ensures better readability of content.
+
+### What Gets Filtered
+
+- **Invisible Unicode Characters**: Zero-width spaces, zero-width joiners, zero-width non-joiners, bidirectional marks, and other invisible Unicode characters
+- **HTML Comments**: Comments that might contain hidden information
+- **Hidden HTML Elements**: Script, style, iframe, and other potentially dangerous HTML elements
+- **Collapsed Sections**: Details/summary elements that might hide content
+- **Very Small Text**: Content with extremely small font size
+
+### Controlling Content Filtering
+
+Content filtering is enabled by default. You can disable it using the `--disable-content-filtering` flag:
+
+```bash
+github-mcp-server --disable-content-filtering
+```
+
+Or using the environment variable:
+
+```bash
+GITHUB_DISABLE_CONTENT_FILTERING=1 github-mcp-server
+```
+
+When using Docker, you can set the environment variable:
+
+```bash
+docker run -i --rm \
+  -e GITHUB_PERSONAL_ACCESS_TOKEN=<your-token> \
+  -e GITHUB_DISABLE_CONTENT_FILTERING=1 \
+  ghcr.io/github/github-mcp-server
+```
+
 ## GitHub Enterprise Server
 
 The flag `--gh-host` and the environment variable `GITHUB_HOST` can be used to set

internal/ghmcp/server.go

@@ -94,7 +94,10 @@ func NewMCPServer(cfg MCPServerConfig) (*server.MCPServer, error) {
 		OnBeforeInitialize: []server.OnBeforeInitializeFunc{beforeInit},
 	}
 
-	ghServer := github.NewServer(cfg.Version, server.WithHooks(hooks))
+	ghServer := github.NewServerWithConfig(github.ServerConfig{
+		Version:                 cfg.Version,
+		DisableContentFiltering: cfg.DisableContentFiltering,
+	}, server.WithHooks(hooks))
 
 	enabledToolsets := cfg.EnabledToolsets
 	if cfg.DynamicToolsets {

pkg/github/filtering.go

@@ -0,0 +1,205 @@
+package github
+
+import (
+	"github.com/github/github-mcp-server/pkg/filtering"
+	"github.com/google/go-github/v69/github"
+)
+
+// ContentFilteringConfig holds configuration for content filtering
+type ContentFilteringConfig struct {
+	// DisableContentFiltering disables all content filtering when true
+	DisableContentFiltering bool
+}
+
+// DefaultContentFilteringConfig returns the default content filtering configuration
+func DefaultContentFilteringConfig() *ContentFilteringConfig {
+	return &ContentFilteringConfig{
+		DisableContentFiltering: false,
+	}
+}
+
+// FilterIssue applies content filtering to issue bodies and titles
+func FilterIssue(issue *github.Issue, cfg *ContentFilteringConfig) *github.Issue {
+	if issue == nil {
+		return nil
+	}
+
+	// Don't modify the original issue, create a copy
+	filteredIssue := *issue
+
+	// Filter the body if present
+	if issue.Body != nil {
+		filteredBody := filtering.FilterContent(*issue.Body, &filtering.Config{
+			DisableContentFiltering: cfg.DisableContentFiltering,
+		})
+		filteredIssue.Body = github.Ptr(filteredBody)
+	}
+
+	// Filter the title if present
+	if issue.Title != nil {
+		filteredTitle := filtering.FilterContent(*issue.Title, &filtering.Config{
+			DisableContentFiltering: cfg.DisableContentFiltering,
+		})
+		filteredIssue.Title = github.Ptr(filteredTitle)
+	}
+
+	return &filteredIssue
+}
+
+// FilterIssues applies content filtering to a list of issues
+func FilterIssues(issues []*github.Issue, cfg *ContentFilteringConfig) []*github.Issue {
+	if issues == nil {
+		return nil
+	}
+
+	filteredIssues := make([]*github.Issue, len(issues))
+	for i, issue := range issues {
+		filteredIssues[i] = FilterIssue(issue, cfg)
+	}
+
+	return filteredIssues
+}
+
+// FilterPullRequest applies content filtering to pull request bodies and titles
+func FilterPullRequest(pr *github.PullRequest, cfg *ContentFilteringConfig) *github.PullRequest {
+	if pr == nil {
+		return nil
+	}
+
+	// Don't modify the original PR, create a copy
+	filteredPR := *pr
+
+	// Filter the body if present
+	if pr.Body != nil {
+		filteredBody := filtering.FilterContent(*pr.Body, &filtering.Config{
+			DisableContentFiltering: cfg.DisableContentFiltering,
+		})
+		filteredPR.Body = github.Ptr(filteredBody)
+	}
+
+	// Filter the title if present
+	if pr.Title != nil {
+		filteredTitle := filtering.FilterContent(*pr.Title, &filtering.Config{
+			DisableContentFiltering: cfg.DisableContentFiltering,
+		})
+		filteredPR.Title = github.Ptr(filteredTitle)
+	}
+
+	return &filteredPR
+}
+
+// FilterPullRequests applies content filtering to a list of pull requests
+func FilterPullRequests(prs []*github.PullRequest, cfg *ContentFilteringConfig) []*github.PullRequest {
+	if prs == nil {
+		return nil
+	}
+
+	filteredPRs := make([]*github.PullRequest, len(prs))
+	for i, pr := range prs {
+		filteredPRs[i] = FilterPullRequest(pr, cfg)
+	}
+
+	return filteredPRs
+}
+
+// FilterIssueComment applies content filtering to issue comment bodies
+func FilterIssueComment(comment *github.IssueComment, cfg *ContentFilteringConfig) *github.IssueComment {
+	if comment == nil {
+		return nil
+	}
+
+	// Don't modify the original comment, create a copy
+	filteredComment := *comment
+
+	// Filter the body if present
+	if comment.Body != nil {
+		filteredBody := filtering.FilterContent(*comment.Body, &filtering.Config{
+			DisableContentFiltering: cfg.DisableContentFiltering,
+		})
+		filteredComment.Body = github.Ptr(filteredBody)
+	}
+
+	return &filteredComment
+}
+
+// FilterIssueComments applies content filtering to a list of issue comments
+func FilterIssueComments(comments []*github.IssueComment, cfg *ContentFilteringConfig) []*github.IssueComment {
+	if comments == nil {
+		return nil
+	}
+
+	filteredComments := make([]*github.IssueComment, len(comments))
+	for i, comment := range comments {
+		filteredComments[i] = FilterIssueComment(comment, cfg)
+	}
+
+	return filteredComments
+}
+
+// FilterPullRequestComment applies content filtering to pull request comment bodies
+func FilterPullRequestComment(comment *github.PullRequestComment, cfg *ContentFilteringConfig) *github.PullRequestComment {
+	if comment == nil {
+		return nil
+	}
+
+	// Don't modify the original comment, create a copy
+	filteredComment := *comment
+
+	// Filter the body if present
+	if comment.Body != nil {
+		filteredBody := filtering.FilterContent(*comment.Body, &filtering.Config{
+			DisableContentFiltering: cfg.DisableContentFiltering,
+		})
+		filteredComment.Body = github.Ptr(filteredBody)
+	}
+
+	return &filteredComment
+}
+
+// FilterPullRequestComments applies content filtering to a list of pull request comments
+func FilterPullRequestComments(comments []*github.PullRequestComment, cfg *ContentFilteringConfig) []*github.PullRequestComment {
+	if comments == nil {
+		return nil
+	}
+
+	filteredComments := make([]*github.PullRequestComment, len(comments))
+	for i, comment := range comments {
+		filteredComments[i] = FilterPullRequestComment(comment, cfg)
+	}
+
+	return filteredComments
+}
+
+// FilterPullRequestReview applies content filtering to pull request review bodies
+func FilterPullRequestReview(review *github.PullRequestReview, cfg *ContentFilteringConfig) *github.PullRequestReview {
+	if review == nil {
+		return nil
+	}
+
+	// Don't modify the original review, create a copy
+	filteredReview := *review
+
+	// Filter the body if present
+	if review.Body != nil {
+		filteredBody := filtering.FilterContent(*review.Body, &filtering.Config{
+			DisableContentFiltering: cfg.DisableContentFiltering,
+		})
+		filteredReview.Body = github.Ptr(filteredBody)
+	}
+
+	return &filteredReview
+}
+
+// FilterPullRequestReviews applies content filtering to a list of pull request reviews
+func FilterPullRequestReviews(reviews []*github.PullRequestReview, cfg *ContentFilteringConfig) []*github.PullRequestReview {
+	if reviews == nil {
+		return nil
+	}
+
+	filteredReviews := make([]*github.PullRequestReview, len(reviews))
+	for i, review := range reviews {
+		filteredReviews[i] = FilterPullRequestReview(review, cfg)
+	}
+
+	return filteredReviews
+}