Program: 25388
Project: 25388
Buggy source:
public void a(Packet130UpdateSign packet130updatesign){
  if (this.e.world.f(packet130updatesign.a,packet130updatesign.b,packet130updatesign.c)) {
    TileEntity tileentity=this.e.world.getTileEntity(packet130updatesign.a,packet130updatesign.b,packet130updatesign.c);
    if (tileentity instanceof TileEntitySign) {
      TileEntitySign sign=(TileEntitySign)tileentity;
      if (!sign.fresh) {
        int x=packet130updatesign.a;
        int y=packet130updatesign.b;
        int z=packet130updatesign.c;
        server.getLogger().severe("String_Node_Str" + getPlayer().getName() + "String_Node_Str"+ getPlayer().getAddress().toString()+ "String_Node_Str"+ x+ "String_Node_Str"+ y+ "String_Node_Str"+ z+ "String_Node_Str");
        this.d.f.a(new Packet1Login("String_Node_Str","String_Node_Str",0,0,(byte)0));
        return;
      }
    }
    int i;
    int j;
    for (i=0; i < 4; ++i) {
      boolean flag=true;
      if (packet130updatesign.d[i].length() > 15) {
        flag=false;
      }
 else {
        for (j=0; j < packet130updatesign.d[i].length(); ++j) {
          if (FontAllowedCharacters.a.indexOf(packet130updatesign.d[i].charAt(j)) < 0) {
            flag=false;
          }
        }
      }
      if (!flag) {
        packet130updatesign.d[i]="String_Node_Str";
      }
    }
    if (tileentity instanceof TileEntitySign) {
      i=packet130updatesign.a;
      int k=packet130updatesign.b;
      j=packet130updatesign.c;
      TileEntitySign tileentitysign=(TileEntitySign)tileentity;
      Player player=server.getPlayer(this.e);
      SignChangeEvent event=new SignChangeEvent(org.bukkit.event.Event.Type.SIGN_CHANGE,(CraftBlock)player.getWorld().getBlockAt(i,k,j),server.getPlayer(this.e),packet130updatesign.d);
      server.getPluginManager().callEvent(event);
      if (event.isCancelled()) {
        for (int l=0; l < 4; ++l) {
          event.setLine(l,"String_Node_Str");
        }
      }
 else {
        tileentitysign.fresh=false;
      }
      for (int l=0; l < 4; ++l) {
        tileentitysign.a[l]=event.getLine(l);
      }
      tileentitysign.h();
      this.e.world.g(i,k,j);
    }
  }
}

Fixed version (ground truth):
public void a(Packet130UpdateSign packet130updatesign){
  if (this.e.world.f(packet130updatesign.a,packet130updatesign.b,packet130updatesign.c)) {
    TileEntity tileentity=this.e.world.getTileEntity(packet130updatesign.a,packet130updatesign.b,packet130updatesign.c);
    if (tileentity instanceof TileEntitySign) {
      TileEntitySign sign=(TileEntitySign)tileentity;
      if (!sign.fresh) {
        int x=packet130updatesign.a;
        int y=packet130updatesign.b;
        int z=packet130updatesign.c;
        server.getLogger().severe("String_Node_Str" + getPlayer().getName() + "String_Node_Str"+ getPlayer().getAddress().toString()+ "String_Node_Str"+ x+ "String_Node_Str"+ y+ "String_Node_Str"+ z+ "String_Node_Str");
        this.b(new Packet1Login("String_Node_Str","String_Node_Str",0,0,(byte)0));
        this.a("String_Node_Str");
        return;
      }
    }
    int i;
    int j;
    for (i=0; i < 4; ++i) {
      boolean flag=true;
      if (packet130updatesign.d[i].length() > 15) {
        flag=false;
      }
 else {
        for (j=0; j < packet130updatesign.d[i].length(); ++j) {
          if (FontAllowedCharacters.a.indexOf(packet130updatesign.d[i].charAt(j)) < 0) {
            flag=false;
          }
        }
      }
      if (!flag) {
        packet130updatesign.d[i]="String_Node_Str";
      }
    }
    if (tileentity instanceof TileEntitySign) {
      i=packet130updatesign.a;
      int k=packet130updatesign.b;
      j=packet130updatesign.c;
      TileEntitySign tileentitysign=(TileEntitySign)tileentity;
      Player player=server.getPlayer(this.e);
      SignChangeEvent event=new SignChangeEvent(org.bukkit.event.Event.Type.SIGN_CHANGE,(CraftBlock)player.getWorld().getBlockAt(i,k,j),server.getPlayer(this.e),packet130updatesign.d);
      server.getPluginManager().callEvent(event);
      if (event.isCancelled()) {
        for (int l=0; l < 4; ++l) {
          event.setLine(l,"String_Node_Str");
        }
      }
 else {
        tileentitysign.fresh=false;
      }
      for (int l=0; l < 4; ++l) {
        tileentitysign.a[l]=event.getLine(l);
      }
      tileentitysign.h();
      this.e.world.g(i,k,j);
    }
  }
}